Protesters march with flares during a demonstration on Tuesday in Marseille, southern France. Daniel Cole/Associated Press

PARIS — Protests and strikes against unpopular pension reforms kicked off again Tuesday across France, with police security ramped up amid government warnings that radical demonstrators intended “to destroy, to injure and to kill.”

Concerns that violence could mar the demonstrations prompted what Interior Minister Gérald Darmanin described as an unprecedented deployment of 13,000 officers, nearly half of them concentrated in the French capital.

After months of upheaval, an exit from the firestorm of protest triggered by President Emmanuel Macron’s changes to France’s retirement system looked as far away as ever. Despite fresh union pleas hat the government pause its hotly contested push to raise France’s legal retirement age from 62 to 64, Macron seemingly remained wedded to it.

The French leader previously used a special constitutional power to ram the reform past legislators without allowing them a vote. His move this month further galvanized the protest movement. Violence has since flared and thousands of tons of stinking garbage have piled up on Paris’ streets as sanitation workers strike.

“Everybody is getting madder,” said Clément Saild, a train passenger at Paris’ Gare de Lyon railway station, where tracks were temporarily invaded and blocked Tuesday by protesting workers.

He said he supports the strikes despite their impact on transportation and other services.

“I am 26, and I wonder if I will ever retire,” he said.

Another passenger, Helene Cogan, 70, said: “French people are stubborn and things are getting out of hand.”

The wave of protests Tuesday marked the 10th time since January that unions have called on workers to walk out and for demonstrators to flood the nation’s streets against Macron’s retirement changes, which are a key priority of his second term as president.

Workers demonstrate with a banner reading “Police mutilates, we don’t forgive” in Nantes, western France on Tuesday. Jeremias Gonzalez/Associated Press

His government argues that France’s pension system will dive into deficit without reform, because of the lower birth rates and longer life expectancy in many richer nations. Macron’s opponents say additional funding for pensions could come from other sources, without having to make workers retire later.

Demonstrations got underway peacefully Tuesday morning, with large crowds in multiple cities. But police braced for violence later in the day. The interior minister said more than 1,000 “radical” troublemakers, some from overseas, could latch on to marches in Paris and elsewhere.

“They come to destroy, to injure and to kill police officers and gendarmes. Their goals have nothing to do with the pension reform. Their goals are to destabilize our republican institutions and bring blood and fire down on France,” the minister said Monday in detailing the policing.

Some protesters, human rights campaigners and Macron’s political opponents allege that police officers have used excessive force against demonstrators. A police oversight body is investigating multiple claims of wrongdoing by officers.

The striking railway workers outside Gare de Lyon marched behind a banner that alleged: “The police mutilates. We don’t forgive!”

Macron’s opponents are urging him to cool tempers by backing down. Union leader Laurent Berger appealed Tuesday for a pause in implementing the retirement reform and for mediation.

“If we want to avoid tensions – and I want to avoid them – what the trade unions are proposing is a gesture to calm things down,” he said. “It must be seized.”

But government spokesman Olivier Veran said mediation wasn’t needed for unions and the government to talk to each other.

The latest round of protests prompted Macron to indefinitely postpone a planned state visit this week by King Charles III.

Veran insisted, however, that France remains a welcoming place for all non-royal visitors.

“Life goes on,” he said.

Jade le Deley and Jeffrey Schaeffer in Paris contributed.