Guards across the country have downed tools following a string of attacks by inmates and scuffles at jails, including Europe’s biggest, Fleury-Merogis just south of Paris.
Unions pushing for better safety and wages have vowed a "total blockade" of prisons on Monday as their dispute with the government worsens.
Overnight France’s justice minister Nicole Belloubet said she would meet with union leaders on Monday in a push to end the crisis.
"The Minister of Justice wishes to resume dialogue immediately," the ministry said in a statement adding it was the responsibility of all sides to ensure that prisons were functioning.
But the latest attack on guards is likely to harden attitudes among the major French prison unions ahead of Monday’s blockade and follows a week of tension and strikes over security and employment concerns.
The male and female guards were attacked in a detention centre at Longuenesse prison near Calais at 6:30 pm, when the cells were still open, according to a prison union official.
"This is once again an attack on the staff, we can not stand it anymore: it’s a daily thing," said Yannick Lefebvre from Ufap-Unsa union.
On Saturday, the CGT and Ufap-Unsa unions rejected proposals to end the standoff.
The third union representing prison guards -- the FO -- has taken a more hardline approach to government talks.
"We are very shocked (by the latest attack). It will only amplify the grumbling and there will be a hardening tomorrow at Longuenesse," said the FO union’s prison inter-regional secretary Julien Martin.
The FO and CGT unions have called for 188 prison institutions to be blocked from 6 am on Monday.
’Tired and furious’
"The staff are tired and furious, the movement will be hard on Monday," warned Christopher Dorangeville, secretary general of CGT’s prison section.
The CGT has said government proposals to end the strike action fall "well short" of their demands, and the Ufap-Unsa, the biggest union representing some 40 percent of prison staff, has backed them.
FO has so far not joined mediation talks and rejected a draft agreement that proposed the creation of 1,100 guard jobs over four years, "including a first tranche of 100 jobs from 2018".
Currently, the prison service employs 28,000 guards in 188 establishments holding about 78,000 prisoners.
On Friday in Borgo on Corsica, three inmates, including one under surveillance for Islamic radicalisation, attacked two guards with a knife, wounding one of them seriously.
On January 11, German convict Christian Ganczarski, a former top Al-Qaeda militant, attacked three officers with scissors and a razor blade at a high-security prison in northern France.
Two other attacks followed in less than a week, prompting guards to launch the nationwide strike.
President Emmanuel Macron has promised to outline plans to overhaul the prison system by the end of February, expected to include facility renovations and expansions to house an additional 15,000 inmates. VNS