In the disturbing video, protesters were seen being knocked to the ground and then kicked – sometimes repeatedly in the head – by men in suits.
Footage from the scene shows two elderly men, believed to be protesters, bleeding from the head – their clothing covered in blood.
Flint Arthur, one of those at the protest against Erdogan, told CNN why they were demonstrating.
‘We are protesting (Erdogan’s) policies in Turkey, in Syria and in Iraq,’ he said, before turning the comments towards the tactics adopted by those supporting the president.
‘They think they can engage in the same sort of suppression of protest and free speech that they engage in Turkey.
Doug Buchanan, a DC Fire and EMS spokesman, said two of those hurt were seriously injured and were taken to hospitals by ambulance