PARIS (Reuters) - French prison guards launched a nationwide strike on Monday in a showdown with President Emmanuel Macron’s government over staffing levels and violence which they say is spiralling out of control in overcrowded jails.

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The strike, which kicked off with pre-dawn pickets, marked an escalation in protests after unions this weekend rejected a government proposal to recruit 100 extra prison warders this year and a further 1,000 before the end of Macron’s mandate in 2022.

Guards burned tyres and pallets outside several of the 188 jails in France ahead of talks hastily convened by Justice Minister Nicole Belloubet.

By midday, police had been sent into four jails to replace absent guards, a prison services spokesman told Reuters. Unions said the authorities would have to deploy additional officers as other guards came off shift.

“We will not be used as cannon fodder. We won’t give an inch,” Yoan Karar, an official for the Force Ouvriere union told CNews. His union wants higher wages and rapid hiring of 2,400 staff.

Macron is under pressure to address the unrest among prison staff after several recent attacks on guards by inmates.

On Friday, riot police clashed with guards manning a picket outside the Fleury Merogis prison, where protests first erupted 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.

The ministry has offered to meet another demand and separate the most violent inmates from the rest of the 70,000 prison population, one of Europe’s largest.

Macron said before protests snowballed that a plan would be presented in February and go beyond existing pledges to build thousands of new prison cells.

France’s prison population has more than doubled since the 1970s. The guards say they no longer have enough staff or equipment to handle violent inmates, notably convicted Islamists and petty criminals who become radicalized while in prison.

They are also demanding improvement on salaries which start at around 1,400 euros ($1,715.56) a month before tax.

Union representative Karar, a guard for 13 years at Fresnes prison on the edge of Paris, said records put the number of attacks on security staff at 4,000 a year.

“You cannot put a guard in charge of 100 or 150 prisoners and just give him a whistle,” said Karar, calling for guards to be armed with taser guns.