Marseilles prosecutor Brice Robin said no Russians had been arrested as they were "highly trained".
"These people were well prepared for ultra-rapid, ultra-violent action," he said.
Fan wears GoPro during violent clashes in France
WHO ARE THE ULTRAS?
The term is short for "ultra-fanatics" and used to refer to right-wing hooligans who actively seek out violence in groups.
Social media accounts show spoof merchandise glorifying violence and pictures of bloodstained flags from other countries after the attacks.
One tweet mocked English supporters for being "transformed from fans to resentful girls". Another post said "Respect for Russian hooligans. Real fighters not fat f***in drinker of Guiness (sic)".
Journalist Andrei Malosolov, co-founder of Russia's Fans' Union told the BBC that unlike other football hooligans, Russians had a distinct lifestyle and were in "top place" in the "hooligan chart" along with Poland.
"Now many people are boxers or into mixed martial arts, and Russian hooligans often follow a very healthy way of life, avoiding alcohol which used to be part of the subculture," he said.
"The English like drinking more, and when they drink they lose quality as fighters and slow down. Our people were more prepared, because of the culture these days."
On Tuesday, Russian supporters on a bus were searched with some taken to detention centres.
Now, authorities fear more violence in the upcoming games between Russia and Slovakia on Wednesday and England and Wales on Thursday.
English Football Association chairman Greg Dyke has written to UEFA asking them to review security arrangements ahead of the game in Lens against Wales.
He also acknowledged English fans were partly to blame for the issues with the Russia game.
"Supporters were able to get in with fireworks and flares, and then let them off, and there was insufficient segregation between the Russian and English fans, particularly given the events of the previous two days," he said.
"While we will be working hard to positively influence [England fans'] behaviour, we have serious concerns around the security arrangements for the city in the next few days."
England manager Roy Hodgson and captain Wayne Rooney have also directly appealed to fans to stay out of trouble, with Rooney urging fans to stay at home unless they have a ticket for the game.
"For the fans with tickets: be safe, be sensible and continue with your great support for the players," he said.
The Russian Football Union has asked its fans to respect the law and "abstain from using fires, laser pointers and other prohibited devices at the stadium".
However Russian politician Igor Lebedev, who also sits on the Russian Football Union executive committee, said he didn't "see anything wrong with the fans fighting."
"Quite the opposite, well done lads, keep it up!" he said. "In nine out of 10 cases, football fans go to games to fight, and that's normal.
"The lads defended the honour of their country and did not let English fans desecrate our Motherland."
Russia's Investigative Committee's head of the media relations Vladimir Markin also said on Twitter perhaps fans were surprised to see "normal men" in reference to the clashes.
"They are used to seeing 'men' at gay parades," he said.
