Witnesses have revealed the terrifying moment that dozens of armed officers stormed a Tube station just minutes after a man in a red tracksuit ran across London Bridge from the scene of the attack.
Six people have died and three terrorists have been shot dead by armed police after they went on a horrific knife rampage in central London last night.
The men, described as being 'of Mediterranean origin', mowed down up to 20 people with a white van hurtling across London Bridge at 50mph on Saturday. One of the casualties is reportedly a police officer.
But earlier in the night, amid confusion and chaos police stormed Monument Station with at least 50 armed officers with dogs seen by witnesses.
Bystanders were told to run with Bank and Monument Tube stations being closed down.
Oliver Jones, a journalist who witnessed the sudden police action, told MailOnline: 'There are probably about 30 to 40 police cars there.
'Police entered Monument Underground station – there were five police dogs then the police cordon was moved back again.
'Earlier before police entered Monument there was a man wearing a red tracksuit who was running.
According to witnesses the attackers were 'randomly stabbing' revellers with 12-inch hunting knives in the nearby Borough Market area of bars and restaurants in what authorities described as terrorist incidents. One man was reportedly stabbed five times in the chest.
Bystanders said the gang, with metal canisters strapped to their chests, smashed pub windows and cut the throats of drinkers, and a 'dark-skinned' man in a red tracksuit 'calmly' stabbed a man three times.
Armed police rushed to the scene where shots were heard and authorities urged Londoners on Twitter to 'run, hide, tell' if they were caught in the 'utter chaos'.
Two suspects were shot dead by a marksman outside the Wheatsheaf pub in Borough Market and one was gunned down and believed to be killed, as the remaining two suspects are on the run.
Terrifying footage from the scene shows police officers shouting 'Clear the scene now!' as panicked pedestrians flee. London Ambulance said multiple resources were attending the area.
The car that the three men were in have veered in an 'S shape' across the bridge and drove towards the Shard and was south of the river. There are unconfirmed reports that it is a B&Q and Hertz van.
One woman said she saw three people with what appeared to be their throats cut at London Bridge. There are also reports that a bystander was shot in the head in the crossfire and at least seven people have been stabbed.
'The men said this is for Allah as they left the van and attacked victims. There were definitely three people sitting at the front of the van,' London Bridge eyewitness Eric Seguenzo told BBC News.
A harrowing video shows Londoner Geoff Ho staggering down the street with a bleeding neck wound after being stabbed at the Southwark Tavern. He was rushed to hospital in an ambulance during the chaos.
Witnesses to the terror attack said there was a stabbing in the Southwark pub venue at the Borough market while others heard at least 12 gunshots in the area.
Twitter users have circulated an image of Mr Ho and claim he is missing after being stabbed at the tavern.
'I need to know if Geoff Ho is ok if anyone can help. Stabbed at Southwark Tavern. Last seen in an ambulance,' Isabelle Oderberg tweeted early on Sunday morning.
Police are advising people who live within the London Bridge cordon to stay somewhere else tonight if they can.
One of the men suspected of being an attacker was pictured lying on the ground after he was shot by the police outside the Wheatsheaf pub in Borough Market. Another man was seen lying on the ground a short distance away.
It has been reported that SAS helicopters have been flown in from their Hereford headquarters to hunt for the deadly duo still on the run.
The bridge is in lock down and the area around it is closed with bus routes being diverted, as armed police and a bomb squad attend the scene and boats search the Thames for bodies - amid reports that people were pushed into the water.
Photographer Gabriele Sciotto, who had been in the area watching the Champions League Final, said he ran towards the scene of the attack after three alleged assailants began stabbing people in the Borough Market area.
He told BBC News: 'I came in after the men stabbed some other men. I ran towards the scene because I noticed this man with this kind of explosive looking belt on his chest, they were running.
'A police officer was trying to put himself between them and the crowd. After that they were almost coming towards me and I tried to run away. Then they were going towards the main street. At that point, I ran towards them.
One witness reported seeing a van crash into a lamppost by the Barrowboy and Banker pub past the bridge.
A bystander said a friend was in Applebee's Restaurant in Borough Market when suddenly the waiters pulled down all the shutters.
There were also claims that a topless man had been handcuffed and taken into custody.
Barman Alex Martinez was forced to take shelter in a bin when a knifeman stormed the Borough restaurant in which he worked.
He said: 'I remember that I was working behind the bar and one man entered into my restaurant and that's it - I remember about the third table, second one, next to the door, a man dropped everything and ran out.
'I just tried to be safe, I jumped down behind a big wall, now I feel my pain in my arm, I feel pain.
'I saw that man with a knife in his hand and after that a man started screaming so I knew something wrong was happening.
He recalled hearing someone crying near his bin and said the two exchanged reassurances.
One man who was in a pub by the Shard told MailOnline: 'I was feet away from getting stabbed.
'Basically lots of people came running inside, we didn't really know what was going on.
He added: 'The bouncers did a really good job, they shut the doors and locked everyone in. There was panic - it seemed like it was literally outside the door. People were coming inside and saying they had witnessed people being stabbed.
Hours after the initial attack two loud blasts were heard near London Bridge although police were said to have looked 'calm' about the explosions.
It is thought that they could have been controlled explosions carried out by officers.
Theresa May called the events in London a 'potential act of terrorism' after reports of a van hitting pedestrians, stabbings and armed police firing shots around the London Bridge area.
'Following updates from police and security officials, I can confirm that the terrible incident in London is being treated as a potential act of terrorism,' May said in a statement.
London Mayor Sadiq Khan has called the terrorist incidents at London Bridge and Borough Market 'deliberate and cowardly', adding: 'There is no justification whatsoever for such barbaric acts'.
Home Secretary Amber Rudd said the London attacks were 'horrific', adding they were 'targeted at people enjoying their evening with friends and family'.
Police responded to a third incident in Vauxhall, south London, which later turned out to be an unrelated stabbing. Officers are telling people 'you must run, hide and tell'.
The attacks in the streets of London come just days after armed troops were pulled off the streets of Britain.
Thousands of soldiers were deployed by the Prime Minister following the bombing at Manchester arena as she raised the UK threat level from 'severe' to 'critical'.
At least one person is believed to have been stabbed in the doorway of the Southwark Tavern in Southwark Street. Drinkers are said to have thrown chairs and glasses at the attacker as he stormed the pub.
Ben and his wife Natalie were in Borough Market near the Southwark Tavern. They told BBC Radio 5 Live that they saw a 'dark-skinned man in a red tracksuit' stabbing a man.
Ben said: 'We saw people running away and then I saw a man in red with a large blade, at a guess 10 inches long, stabbing a man, about three times.
'I was across the road about 15m away. [The attacker] was dark-skinned and had a red tracksuit on.
Police are treating injured people and carrying them away at the end Thrale Street. Members of the public were told by police to 'run as fast as they could' westbound.
Kumi de Costa was caught up with her two friends at the incident in Borough Market. She told the BBC: 'The cab driver turned into the market and we got stuck right in the middle of the shooting we were in a one-way street and couldn't turn around.
'There were loads of shots being fired. Two people were on the floor behind the church with two or three people leaning over them.
'About 50 police were pointing guns at us - the cab driver had the laser pointed right at them, our hands were up, we were trying to get out so they shooed us away.
'A man was coming out of the restaurant, he had a napkin on his neck with blood pouring out, there was another man lying on the floor. I don't know if he was in the recovery position or dead.
'We weaved through little side streets where the police were telling us to go to Blackfriars Bridge and we could see people looking over the side; people had maybe jumped over the bridge.
Bursts of gunfire were heard as witnesses described how one man was arrested after police stormed towards a house in Southwark.
The Asian man in his mid thirties had his hands tied behind his back as up to 30 police frogmarched him down the street shouting at people to get back.
'They had shields and were wearing masks and were running across the street shouting at one another.
'I heard what sounded like short bursts of gunfire. Suddenly they started shouting at us 'run away' ' get back' and people really were running for their lives.
'About 15 of us were running down Borough High street toward London Bridge followed by 30 armed police. They were spread put across the street.
'They had a man. There were four police either side of him and others crowded round. They had his hands tied behind his back.
'He was Asian man, about 5ft 6in, dark hair, mid thirties with stubble. wearing a dark jacket. He was being frogmarched quickly down the street. They crowded round him at the first corner then we were all ushered away as they extended the cordon.
A security guard who oversees a number of pubs in the area has told the BBC he saw four people stabbed by three attackers.
The man, who was deeply shocked and asked not to be named, said he was at the Market Porter pub when a colleague at another bar said there was a stabbing at the Borough Bistro pub nearby.
He said he went towards this pub and saw that 'everybody started running' and there was screaming.
The eyewitness added that he saw three attackers, one of whom had a long knife and stabbing people, including a girl in her early 20s.
Alex Shellum was in the Mudlark pub with his girlfriend and two friends, underneath London Bridge, at the time of the incident.
'At around 10pm an injured woman came into the pub seeking assistance. She was bleeding heavily from the neck - it appeared that her throat had been cut. People sought to stem the bleeding and the pub was closed.
They sought refuge with some others at Bill's restaurant in the market.
There are about 20 people being treated at the Andaz Hotel near Liverpool Street station.
One woman has been stretchered into an ambulance along with a young man with a heavily bandaged and bloodied head. Most of the wounded have now been moved.
People staying in the Premier Inn Bankside have been evacuated across Southwark Bridge. Dozens, including children, were brought across the bridge by police after the fire alarm in the hotel went off, according to one.
Samuel Templeton, from Belfast, one of the guests in the hotel, said there was a heavy police presence and they were told to cross the bridge in single file. The guests have since been escorted to a nearby hotel.
Jeremy Corbyn has tweeted: 'Brutal and shocking incidents reported in London. My thoughts are with the victims and their families.' #LondonBridge'.
An hour after the attack witnesses reported seeing 'large numbers of marked and unmarked vehicles' speeding around the streets south of London Bridge amid a hunt for the suspects.
Others said they had been told to 'run' by armed officers or escorted under guard through empty streets in groups.
One eyewitness who wished to remain anonymous told MailOnline: 'I was in Arabica restaurant with a friend in borough market.
'Suddenly there was commotion and people were screaming. Security guards were yelling at people to get back from the window. About 50 people piled into the restaurant. Then I heard two separate bursts of gunfire and people rushed into the restaurant kitchens to hide. It was utter chaos.
Several police officers have stormed a pub opposite the bridge and told people to 'get down' and sit on the floor.
He said: 'They just had these long blades, about 12 inches long. They just went randomly along Borough High Street stabbing people. A young girl got stabbed in the chest, she was laying there - it's so sad.
'I thought, 'I'm gonna try and hit him, I'm gonna try and knock him down'. I spun the cab round, I was about to ram one of them, but he side-stepped and three police officers came running towards them with their batons drawn.
'He's veered across the road towards the right hand of where Southwark Cathedral is and rammed it where the steps are.
'He just rammed it towards them, wedged it in between the lamppost and the steps and so he's hit people there.
Tony Murphy, who has a flat opposite Southwark Bridge, said he heard 'rapid gunfire'.
He said: 'I'm actually former military. I heard what was significant gunfire.
'At first I thought it was fireworks but it was so rapid I recognised what it was.
Holly Jones, a BBC reporter at the bridge when the incident happened, said a van had swerved off the road into a crowd of pedestrians.
'A white van driver came speeding – probably about 50mph – veered of the road into the crowds of people who were walking along the pavement,' she told BBC News.
Ms Jones later reported seeing a man being arrested by police. She said he was handcuffed and had his shirt off.
Witness Alessandro told the BBC that he saw a van at the end of London Bridge with no driver inside and described the 'five or six' people hit as 'very young'.
He said: 'I was going up the stairs of London Bridge Station. I saw this van going left and right trying to hit as many people as he could. I tried to help people.
'At the end of the bridge we saw a van but we didn't see anyone in the van.
'I think [the driver] went to the end of London Bridge. We didn't see the van stop because we were trying to help people.
'Everything was confused. There were five or six people [hit]. Three of them were conscious. One of them was not talking at all. He was just down.
Another taxi driver named only as Paul said: 'I was just going over London Bridge and on the left hand side it looked like someone had been knocked off a bike.
'A few yards on I saw another person laying down and a woman screaming.
Nick Archer, who was in the London Bridge area, told Sky News: 'We came out (of a bar) on to the road and looked and looked to my left and there is a guy, I thought he was just drinking but he was lying on the floor.
London Bridge and the area around it has been closed due to a 'major police incident', TFL said.
London Bridge station has been closed and no trains are expected until the end of service.
Holly, who said she was just two metres away from being hit by a white van, described the chaos on London Bridge after the attack.
She told Radio 5Live: I was probably two metres away. I saw it hit the people in front of me. I feel just so lucky now.
The BBC's Holly Jones spoke to a French woman who had been injured in the incident.
She told Ms Jones: 'I don't know where those other two people are. So the police are checking the Thames.
Witnesses told the BBC that a white van veered off the road on London Bridge and hit five or six people.
'Horrific scene at London Bridge. Bodies strewn over the pavement, B&Q van mounted the pavement. I feel sick,' one witness wrote.
'On a boat travelling under London Bridge. Buses stopped. Police lights everywhere and boats checking the water. Please let everyone be okay!' another added.
London Bridge is closed both ways due to a police incident, Tfl said, warning the public to avoid the area.
Scotland Yard said officers were at the scene and they would update with further information.