The main CGT union said attacks against guards were becoming more common and intolerable.
The penal population was becoming “increasingly vindictive, aggressive and violent”, they said.
A total of 18 prisons were blocked after guards set fire to tyres and built barricades in front of the entrances on Wednesday morning, although the number later reduced to 10.
Demonstrators said no staff or visitors would be allowed into the prison as they protested about the dangers they face from radicalised prisoners, The Local website reported.
The protest came a day after two guards were stabbed with a ceramic knife by a prisoner, whose wife was visiting.
The inmate locked himself in the room afterwards but no hostages were taken. Along with his wife, he was later shot in a police raid. His wife died from her injuries.
French officials described the stabbing as a “terrorist attack” and the country's justice minister Nicole Belloubet said the knife may have been smuggled in by the prisoner’s wife.
In January last year, a prisoner convicted of terrorism wounded three prison guards at Vendin-le-Vieil in northern France.
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