A bus carrying Russian fans has been detained near the French city of Nice amid concerns over violence after supporters of Russia and England clashed last week before and after the two nations' Euro 2016 meeting.
A local official says a bus carrying 29 Russian fans was stopped by police after leaving a hotel near the Cote d'Azur town of Mandelieu-La Napoule on Tuesday.
Prefecture communications chief Ariane Parachini says police stopped the fans to see whether any hooligans were among them.
An unspecified number have been taken to detention centres, a possible prelude to deportation.
Russian Embassy spokesman Sergei Parinov confirmed the episode.
"They want to deport almost 50 people including women who did not take part in anything," Russian Supporters Union president Alexander Shprygin told Reuters.
"The police are making up for their mistakes three days ago [in Marseille]. We are in a bus in Cannes and we have been blocked in by riot police. We are not going anywhere for the time being."
Shprygin added that the Russian consul later arrived on the scene.
The group of Russian fans were set to be thrown out of France, AFP reported, because authorities fear they will cause more trouble at Euro 2016.
Francois-Xavier Lauch, a local official in the Alpes-Maritimes area, said police are trying to establish if any of the Russians fans are on a list of supporters who are "considered a risk."
French Prime Minister Manuel Valls had previously said on Tuesday that some supporters were going to be deported following the violent clashes that have taken place around Euro 2016.
"[Some] will be deported because some people cannot stay on national territory," he is quoted by Reuters as saying.
The Russian supporters were reported to be on their way to Lille, where their country play Slovakia on Wednesday.
England face Wales the next day in nearby Lens, raising the prospect of more clashes between the two sets of supporters.
French authorities say a 2,400-strong security force is being deployed in Lens as the town prepares for an influx of 40,000 to 50,000 England and Wales fans for Thursday's Euro 2016 game.
The policing operation in Euro 2016's smallest host city and its 35,000-capacity stadium has been intensified after clashes involving England and Russia fans around their opening Group B game in Marseille on Saturday.
Regional administration head Fabienne Buccio says 1,200 police officers and the same number of private security guards will be in Lens, whose population can fit in its Stade Bollaert-Delelis.
Police will be at the stadium to help separate fans, with UEFA having acknowledged there were segregation problems at Marseille's Stade Velodrome on Saturday.
Buccio says supermarkets around Lens will be banned from selling alcohol on Wednesday and Thursday.
Russia have been fined €150,000 and handed a suspended disqualification from Euro 2016 over crowd disturbances at the game against England, UEFA has announced.