The Russian football fans behind the violence surrounding the Marseille fan violence were "trained fighters who kill", Ukrainian President Petro Poroshenko said during a visit to France on Tuesday.

"I cannot rule out that they were prepared. They were trained fighters who kill," Poroshenko told French television ahead of a meeting with his French counterpart Francois Hollande.

Two Britons remain in a coma in hospital after being seriously injured in the Marseille mayhem ahead of the June 11 Euro match.

They were among 35 mostly British fans hurt in the three days of violence.

Three Russian fans were jailed for up to two years for their role in the chaos, while six England fans were jailed for up to six months.

French prosecutors said the Russian fans in Marseille had targeted England supporters in an orchestrated "hunt".

Twenty Russians were expelled from France, including far-right fan leader Alexander Shprygin -- who is expected to be expelled for a second time on Tuesday after he sneaked back into the country to watch his country play, police said.

Russian President Vladimir Putin has described the violence as a "disgrace", but also said he could not understand "how 200 of our fans could beat up several thousand English".

Poroshenko said he hoped to head to Marseille later Tuesday to watch the Ukraine side take on Poland after it lost to Germany and Northern Ireland in its first two matches.

He said he hoped to "give a little hope to our team".

Russia is under EU economic sanctions for failing to make progress on resolving the conflict pitting pro-Moscow rebels against Kiev forces in eastern Ukraine. Russia signed up to a ceasefire accord signed in February 2015 but it has yet to be fully implemented.