The US has made a complaint to Turkey after violence erupted between protesters and Turkish security personnel in Washington, DC.
Two people were arrested and 11 were injured in protests outside the Turkish ambassador's residence amid President Recep Tayyip Erdogan's visit.
Video footage of the clash on Tuesday showed men in suits charging past police to kick and punch protesters.
But the Turkish Embassy said the demonstrators were aggressively provoking Turkish-Americans who had gathered to greet the president, and they in turn responded in self-defence.
The US State Department released a statement saying it was "concerned by the violent incidents" and confirmed Turkish security guards were involved.
"Violence is never an appropriate response to free speech, and we support the rights of people everywhere to free expression and peaceful protest," the statement read.
"We are communicating our concern to the Turkish government in the strongest possible terms."
Mr Erdogan, who met President Donald Trump earlier in the day, was visiting Turkish ambassador Serdar Kılıç's residence when the scuffle broke out.
Washington's Metropolitan Police Department said it had arrested two US residents Ayten Necmi, 49, and Jalal Kheirabadi, 42, over the incident. It was unclear if they were members of Mr Erdogan's security.
Police Chief Peter Newsham said on Wednesday the violence was "not something we tolerate in our city".
He added several of Mr Erdogan's security personnel were armed with guns, which made the incident especially "dicey" for local police officers trying to keep protests peaceful.
House Foreign Affairs Committee Chairman Ed Royce also sent a letter to Attorney General Jeff Sessions and Secretary of State Rex Tillerson urging them to take action over the clashes.
"To send a clear message that these acts of violence will not be tolerated, I ask that you immediately look into this matter and bring all appropriate criminal charges before these individuals leave the United States," Mr Royce wrote.
"Agents of foreign governments should never be immune from prosecution for felonious behaviour."
Washington Mayor Muriel Bowser said it was "an affront to DC values and our rights as Americans".