French prison guards vowed to “totally block” the country’s jails on Monday as they launched a rare nationwide strike over staffing levels following several attacks by radicalised inmates.

The guards burned tyres and erected barricades in front of several prisons as unions claimed 115 of France’s 188 prisons were blocked, while penitentiary authorities put the figure at 50.

Yesterday’s strike marked an intensification of protests, which erupted after a convicted al-Qaeda extremist attacked guards in a high-security facility with a razor blade, injuring three of them.

Guards complain that rules are too lax for violent and radicalised inmates in French prisons, reputed to be a hotbed of Islamic extremism.

Of France’s 70,000-odd prisoners, some 504 are convicted or awaiting trial on terrorism charges and 1,200 others are under surveillance for radicalisation.