Police on Tuesday detained 43 Russia fans suspected of taking part in clashes with England supporters in Marseille at the start of the Euro 2016 football tournament, and two cities in northern France imposed alcohol bans in a bid to avert more hooliganism.
UEFA said Russia would be thrown out of the tournament if there was a repeat of the violence by Russia fans which marred the end of last Saturday's match against England.
Despite the measures, a small group of Russian and English fans scuffled in the northern city of Lille as thousands of supporters arrived in the area for the next round of matches.
Lille is seen as a potential trouble-spot as Russia play Slovakia there on Wednesday and England fans are also congregating there ahead of their match against Wales in nearby Lens on Thursday.
The violence between rival fans has marred the start of the 24-nation championship and given an extra headache to police and security forces already pre-occupied with guarding against any Islamist militant threat.
The detentions were made after riot police surrounded a bus packed with Russia fans near Cannes on the French Riviera as it headed north. After some argument, the 43 Russians were taken into custody, police said.
"There are clear signs that some of them took part in unacceptable violence in Marseille," local police chief Adolphe Colrat said.
Alexander Shprygin, the head of a Russian supporters group, denied that any of the fans in the bus were involved in the Marseille clashes.
Anti-racism groups have accused Shprygin, a self-described nationalist who was photographed as a young man making what looked like a Nazi salute, of having links to Russia's shadowy far-right movement. He has dismissed the allegations.
UEFA on Tuesday handed down a suspended disqualification on the Russian Football Union in response to attacks by masked Russian supporters on England fans at the end of the 1-1 Group B draw at the Stade Velodrome in Marseille on Saturday.
The governing body said the disqualification would take effect if the fans caused more trouble inside a stadium at any of Russia's remaining matches. It also fined Russia 150,000 euros ($168,300).
Russian Sports Minister Vitaly Mutko said Russia, which will host the 2018 World Cup, would not appeal against the sanction.
"The punishment is excessive, but we cannot influence it," he said. "There is no sense to appeal. But what (has) the team has to do with that? It is not guilty."
The ruling only applied to violence inside a stadium, despite three days of clashes between English, Russian and French fans in the Mediterranean port city before and after the match.
In that violence, fans wielded iron bars, kicked and punched their rivals, and hurled chairs and bottles in city streets. Police responded with volleys of tear gas and baton charges.
Fifteen fans were arrested. Five England fans have so far been sentenced to jail terms of between one and three months and a Frenchman received a two-year term.
No Russians were arrested, although Marseille prosecutor Brice Robin said about 150 Russians were part of a well-organised hooligan gang.
UEFA said on Sunday it could throw England or Russia out of the tournament if violence continued outside.
"We will implement additional corrective measures for the games coming up in Lens and Lille and we hope that those measures will be sufficient to avoid any other crowd trouble during the matches," a spokesman said.
The regional police chief in Lille said the sale of alcohol would be banned from Tuesday evening until Friday morning and bars in the centre would be closed from midnight Wednesday until Thursday evening.
In Lens, the police chief said alcohol sales would be prohibited from Wednesday 0600 (0400 GMT) to Friday 0600 in shops, supermarkets close to car parks and petrol stations serving between Lille and Lens.
Trouble flared briefly in Lille when a small group of Russians appeared to provoke English fans in a bar near the central train station, Reuters photographers said.
The English responded by throwing chairs, but the situation was calming down when police arrived.
Prime Minister Manuel Valls said people who had been sentenced in relation to fan violence would be deported.
"They are not wanted on our national territory due to their behaviour," Valls said.