The prison guards in France are in hospital after they were attacked at Borgo jail on the island of Corsica when three prisoners charged at them.
Prison guards have also clashed with riot police during a strike over their security concerns.
The clash happened outside a prison close to Paris and highlighted the security problems and radicalisation inside the overcrowded French facilities.
French police were forced to fire tear gas to break up a picket line of striking prison guards outside Europe’s biggest prison.
Around 150 prison guards had set up a wall of burning tyres to stop their colleagues from getting to work.
The unions decided to continue with industrial action despite talks to resolve the issues and a pledge made by President Emmanuel Macron to improve security at French prisons.
Justice Minister Nicole Belloubet described it as “intolerable” and flew to Corsica to visit the prison on Friday afternoon.
Around 500 of the 70,000 inmates in French prisons have been sentenced for crimes connected with Islamist terror.
One of the guards has suffered a stab wound to the neck during the knife attack and the other to the head, but neither of their lives are in danger.
Maxime Coustie, a representative of the union l’Ufap-Unsa Justice, said: ”This is a big assault, one of the two guards was unconscious and the attacker is a prisoner who already was known for his bad behaviour.”
According to Ms Coustie, one of the attackers shouted “Allah Akbar” when committing the attack.
One of the attackers was in his thirties and serving a sentence for intentional assault, which resulted in death without intent following an incident in a disco in 2012.
There have been three other attacks in the same prison in Corsica, which has raised fears about how French prison authorities deal with dangerous prisoners.
The guards have accused the government of doing too little to counter the spiralling violence and Islamist activism inside the overcrowded jails.
Talking of the clashes with the police, jai guard Thibult Capelle said: “We’re fed up. We’re taking a thumping inside and now we’re being thumped outside.”
The protests at Fleury Marogis prison and at many other prisons began a week ago, after an Islamist militant jailed over the killing of 21 people in Tunisia in 2000 slashed guards on the head and torso with a pair of scissors in northern France.