Video footage show brawls between rival England and Russian supporters and missiles being thrown in the centre of the host city in southern France.
Two England fans are believed to be fighting for their lives, one of whom suffered cardiac arrest after being was attacked by a mob of Russian fans.
Five other people have been injured in the scuffles and six people have been arrested.
Riot police clad in heavy body armour deployed tear gas against English fans for the second time in just three days as clashes between fans reached boiling point.
They have also used water canons in a desperate attempt to bring the fighting fans under control.
Shocking clips show supporters running riot in the city centre while thugs punched and kicked floored fans.
Some witnesses describing the scene as like a "battlefield" and said Britons were being targeted by groups of Russian gangs.
Broken glass lay strewn across the square as the police fired tear gas into the crowds causing them to run.
One Englishman was heard shouting at French firemen at the scene: “It’s because of your country, it’s a f***ing disgrace”.
One fan said police were “nowhere to be seen for about 15 minutes” as fans caused havoc in the streets.
Another said: "It was the Russians that sparked it all off. A whole gang of the Russians came right into the middle of everything and started throwing punches."
Fans with bloody fans were seen being treated as the clashes raged on, with chairs from outside bars and cafes being smashed apart and used as weapons.
European football body Uefa, which organised the tournament, has a statement saying it "firmly condemns" the incidents in Marseille.
A spokesman added: "People engaging in such violent acts have no place in football."
British police also understood to be "very frustrated" by the actions of their French counterparts.
A senior British police officer today met with French authorities to push for more tolerant methods, Express reported.
212-11