A total of 557 "violent supporters" have been arrested so far at the European Championship, France's interior minister said Monday.

Speaking after a security meeting with local organizers and government officials, Bernard Cazeneuve said some of the troublemakers were given "very firm prison sentences."

The most visible violence at Euro 2016 occurred in Marseille in the opening days of the monthlong competition when England fans, Russia supporters and local youths clashed with each other and French riot police. Tear gas and water cannons were used to break up the trouble.

"With the exception of the first match in Marseille, which led to violence in the city center, the measures taken immediately after this match in liaison with UEFA, but especially with the countries from which these supporters were coming, have enabled us to avoid new acts of violence, new fights in the center of the host cities," Cazeneuve said.

In a statement, the government said 21 fans have been sent to jail and another six have been given suspended prison sentences. French authorities have ordered a further 25 supporters to be deported.

The hooligan threat at Euro 2016 comes amid heightened security in France after the Nov. 13 attacks in Paris, which claimed 130 lives.

Cazeneuve said that while the main focus "remains the terrorist threat, our objective is to continue mobilizing all our forces and all our means, so that this competition can take place in the best possible conditions — even though, again, the constant mobilization ... doesn't mean there is zero risk."

The 24-team tournament which started June 10 ends July 10.