-- Anarchists hijack May Day rally, attack police

-- Police arrest more than 200 people

-- Cars torched, shop windows smashed

-- Macron vows to bring culprits to justice

Hundreds of masked and hooded anarchists smashed shop windows, torched cars and hurled cobblestones at riot police on Tuesday, hijacking a May Day rally by labour unions against President Emmanuel Macron's economic reforms.

Riot police used teargas and water cannon to disperse the protesters. Paris police chief Michel Delpuech said more than 200 demonstrators had been arrested and four people were lightly injured in the clashes, including a police officer.

"I condemn with absolute firmness the violence that took place today and derailed the May Day processions," tweeted Macron, who was on a visit to Australia.

"Everything will be done so that the perpetrators are identified and held responsible for their actions."

Authorities said around 1,200 protesters, many garbed in black, had turned up on the sidelines of the annual May Day demonstration. The protesters were from far-left anarchist groups known as Black Blocs, police said.

Government spokesman Benjamin Griveaux criticised the protesters for covering their faces. "When you have sincere convictions, you demonstrate with your face unmasked," he said. "Those who wear hoods are the enemies of democracy."

Chanting anti-fascist slogans and waving Soviet flags and anti-government banners, the protesters smashed windows of businesses, including a Renault garage and McDonalds restaurant near the Austerlitz train station in eastern Paris.

They also ransacked shops and scrawled anti-capitalist graffiti on walls before eventually being dispersed by police.

AVOIDING CASUALTIES

David Le Bars, a police union official, told BFM TV that security services had decided to let the protesters smash things rather than engage them to avoid casualties on either side that could exacerbate tensions.

"They came to hit capitalist symbols and burn cops. When you come with Molotov cocktails, it's to burn cops," he said, citing clashes on May 1 last year in which one police officer was seriously burnt.

Unions put the number of peaceful protesters at Tuesday's main May Day rally in Paris at about 55,000, though police put it at around 20,000. The numbers were relatively small compared to other recent demonstrations.

Police said the Black Blocs had mixed into a smaller demonstration of around 14,500 people which took place alongside the official union rally.

Tuesday's clashes come amid mounting union discontent with Macron's plans to reboot France's economy and spur jobs growth by loosening labour regulations.

Under a union campaign to foil Macron's reforms, railway staff have begun three months of nationwide rolling strikes aimed at halting a planned overhaul of state-run railway SNCF.

Speaking in Australia earlier on Tuesday Macron, a former investment banker who swept to power a year ago, reiterated that he would not back down on his reform agenda.

Opposition conservative and far-right politicians accused Macron's government of being insufficiently prepared for the violent protests and criticised it for not cracking down more heavily on anarchists.