Nord: The head of Britain`s Euro 2016 policing operation on Sunday said Russian football fans attacked their English rivals wearing gum shields, martial arts gloves and carrying knives.
Assistant chief constable Mark Roberts told Britain`s Guardian daily the clashes in Marseille were the most serious he had seen in 10 years of investigating football violence.
Roberts admitted "a small minority" of England fans were out to cause trouble, but said there were hundreds of "Russian troublemakers".
"Our spotters in Marseille saw them putting in gum shields and putting on martial arts gloves and bandanas before attacking England fans in the port," Roberts was quoted as saying.
"We know some were carrying knives because one England fan was stabbed. They wore a kind of uniform -- all in black T-shirts and clothing and most carried bum bags, possibly to conceal weapons," he told the Guardian.
"When they began their assaults they were extremely well orchestrated and came into the square seeking confrontation with England fans or anyone else in their path.
"Speaking candidly, it is clear there was a small minority of England fans who were in Marseille to cause trouble. Some of the English were guilty of anti-social behaviour," he said.
"But there was a far larger hard core of Russian troublemakers we would estimate at around 300.
"They targeted English fans when the majority of them were decent people in Marseille to enjoy a drink and the football," he added.Roberts warned about possible clashes in Lille later this week when the two teams will be playing near each other, saying "Our primary concern going forward is for the safety of UK citizens at later stages in the tournament."
He said video evidence collected by British police "spotters" would be handed over to French authorities to track down Russian hooligans.
"Our original intention was to use this kind of evidence against England troublemakers, but we are equally anxious to see Russian hooligans brought to book and will cooperate fully with French authorities investigating," he said.
Geoff Pearson, a senior lecturer in criminal law at Manchester University who was in the Marseille Old Port area during Saturday`s violence, also blamed Russian hooligans.
He told the Daily Telegraph there had been a "carnival atmosphere" among England fans in the Old Port until bottles were first thrown at them.
Some English fans threw bottles back and the situation escalated, said Pearson, who specialises in the study of football violence.
He said French police made the mistake at that stage of deploying in full riot gear after which there was "classic crowd escalation".
"With every next bottle thrown an extra canister of tear gas was fired and it degenerated so quickly. When you thought it couldn`t get any worse, the Russian ultras arrived, 100-150 of them, organised and running around the back streets attacking the English fans," he said.
"The anger from the England fans I spoke to towards the police for their failure to protect them was amazing," he said, adding: "Your average England fan was in fear for their lives".