Thousands of people took part in Sunday's march on the French Mediterranean island of Corsica, in solidarity with independence militant and convicted murderer Yvan Colonna, himself grievously injured in a recent attack by a fellow prison inmate. The suspected attacker is facing terrorist charges and an investigation is underway.
The police estimated the number of participants in Sunday's protest in Corte at 4,200. March organisers said 15,000 people took part.
Banners in French and Corsican read "Bless you Yvan", "France Shit!" and "French State Assassination".
Local government leader Gilles Simeoni, who took part in the protest, said people were angry and unhappy at the treatment of Colonna. "They don't understand," he said. "Paris would do well to listen."
There were violent clashes between police and some demonstrators as the otherwise peaceful protest came to an end.
Stones and other projectiles were thrown at the security forces. They replied using tear gas and water cannon.
The ambulance services said they had treated 25 people for injuries, 15 of them needing hospitalisation, but none in serious condition. Four police officers were injured.
There were four arrests.
On Monday, several schools on the island were blocked in protest over the Colonna affair.
For years, Colonna's supporters have demanded that he be imprisoned in a Corsican jail, to facilitate visits by members of his family. Transfer requests have always been refused.
Colonna attacker under scrutiny
Meanwhile, more details have emerged surrounding the violent attack on Yvan Colonna last Wednesday, supported by closed circuit camera footage.
Serving a life sentence for the 1998 murder of Corsican police chief, Claude Erignac, Colonna, was attacked and strangled by a fellow detainee in the mainland prison near Arles while he was working out.
Colonna remains in a coma in a hospital in the southern French city of Marseille. He is 62 years old.
"Once again, islamist fanaticism has been at the centre of another terrorist crime in our country," Jean-François Ricard, the prosecutor in charge of the National Anti-Terrorist Prosecutor's Office, told the press on Sunday.
The 35-year-old suspect in the attack, identified as Franck Elong Abe has formally been charged with "attempted murder and terrorism" and will be the subject of further investigation.
The inquiry will "retrace in detail the background of the attacker, to determine his contacts, notably those who shared his ideology, and to shine a light on the interactions he had which may have played a role in the attack," Ricard said.
It is alleged that the accused attacked and injured Yvan Colonna because of the Corsican nationalist's "blasphemous statements".
Several other prisoners in Arles convicted on terrorism charges have been questioned by police investigating the attack.
The prosecutor underlined that Abe had shown violent behaviour towards himself and others and that there had been "numerous" incidents involving violence in the first 5 jails where he had been incarcerated.
