Penitentiary staff demonstrate about long-running complaints at Fesnes prison outside Paris. Picture: Thibault Camus/AP

Paris - French riot police broke up a jailhouse picket on Wednesday that threatened to disrupt the trial of a man who is suspected of housing the head of a militant Islamist hit-squad that killed 130 people in attacks in Paris in 2015.

The picket was one of dozens nationwide by wardens striking over pay and inmate violence in France's overcrowded prisons, a protest that has snowballed into a full-blown showdown with the government of President Emmanuel Macron.

With the prison guards digging in, the stand-off is turning into a survival test for Justice Minister Nicole Belloubet, a high-flying law lecturer appointed by Macron last June following his election victory.

Union representatives stormed out of talks with Belloubet on Tuesday, describing her offer of 30 million euros in financial incentives as "bonuses for slit throats".

Wednesday's police operation at the Fresnes prison near Paris was ordered after threats by prison wardens to disrupt the transfer of Jawad Bendaoud to court, where he faces trial in connection with the deadly militant attacks of 2015.

Bendaoud is accused of providing the flat where Abdelhamid Abbaoud hid after he and a group of other gunmen and suicide bombers killed 130 people on November 2015.

Bendaoud's arrest was broadcast live and he pleaded innocent to the cameras before being carted off by police. He faces six years in jail if convicted of taking money for supplying the hideout.

Two-thirds of France's 188 prisons were being disrupted by work stoppages and pickets on Wednesday morning, according to an official count.

Among the demands of the striking prison guards is that militant Islamist convicts -- those convicted of terrorism-related offences - be isolated from other prisoners, saying that some inmates are becoming radicalised through contact with them.

The wardens also want more money for a job they say is becoming increasingly dangerous and equipment such as taser guns to help ensure order.

The protests began on Jan. 12 after an al Qaeda convict jailed over killings in Tunisia stabbed and injured two wardens with a pair of scissors in northern France.

In some cases over the past 12 days, police have been sent into prisons to do the job of the striking wardens, and prisoners have been forced to spend more time in their cells.

Some jail cells house as many as three or four inmates in a space of 10 square metres (yards).