Antifa's Washington DC leader has been charged over a mob attack on two innocent US Marine reservists which involved 'ethnic intimidation' in Philadelphia.

Joseph Alcoff, 36, is said to have been part of a gang of 10 Antifa activists who allegedly maced, kicked and hurled racist slurs at Alejandro Godinez and Luis Torres.

Two of the protesters - Thomas Massey and Tom Keenan - have been on trial over the incident where they accused the Marines of taking part in a right-wing 'We are the People Rally' in the city.

Alcoff's 17 charges include counts of aggravated assault, ethnic intimidation, conspiracy and terroristic threats, and one count of robbery while inflicting serious bodily injury.

Joseph Alcoff, 36, also known as 'Chepe' or 'Jose' is said to be Antifa's Washington DC chief and was involved in the attack in Philadelphia when the group took on two innocent US Marines

Protesters gather on Independence Mall in Philadelphia in response to the 'We the People' rally across the street. There is no suggestion anyone pictured was involved in the violence

Protesters Thomas Massey (left) and Tom Keenan (right) have been on trial for their involvement in the alleged attack

Torres informed the police that Alcoff was one of those who was involved in the attack after reading a news article which connected Alcoff to Keenan, the Daily Caller reported.

The Marine then provided images he had taken during the attack and the investigators agreed that it was indeed Alcoff.

Alcoff, also known as 'Chepe' or 'Jose,' was previously arrested alongside Keenan - who is allegedly Antifa's captain in Philadelphia - for rioting in New Jersey in 2011, the Daily Caller said.

Jurors at the Massey and Keenan trial in December heard how the Marines were asked 'Are you Proud Boys?' - alluding to a right wing group.

But the marines didn't understand the reference and replied: 'We are Marines.'

Massey and Keenan then allegedly called them 'Nazis' and 'White Supremacists' before the mob started punching and kicking them and even attacked them with mace, reported Philadelphia Magazine.

Godinez said that he was 'bewildered' when they called him a White Supremacist and blurted: 'I'm Mexican!'

Keenan then allegedly made racist insults against him, calling him a 'spic' and 'wetback'.

Godinez told the court he was viciously beaten and stomped on by the men as the group chanted 'f*** him up' as though they were in a soccer stadium.

He told the court they laughed while he could have died.

When the group ran away, Godinez tried to call 911, but was too injured from the mace to use his phone, he said.

Antifa protesters on 17 November. There is no suggestion anyone pictured was involved in the violence

Torres said he was punched 'with full force' and could only put his hands in front of his face to protect himself from the larger men.

Keenan's lawyer described the incident as a 'tussle'.

Massey and Keenan were facing trial on aggravated assault and conspiracy charges which they deny.

Meanwhile Alcoff's lawyer said he denies the charges against him and he is currently out on $15,000 bail.