A man has been arrested on suspicion of attempted murder amid reports a suspect was seen wielding "a massive machete" at a railway station in south London.
Police were called to Tulse Hill station during evening rush hour just after 18:30 GMT, British Transport Police (BTP) said.
In the course of the arrest a Taser was discharged, according to a BTP statement.
One witness @Vikjas85 tweeted: "Man at Tulse Hill Station with a massive machete just been tasered by the police."
BTP said there were no reported injuries and the suspect was also arrested on suspicion of possessing an offensive weapon.