French "yellow vests" marched through Paris and other cities on Saturday in protest against high living costs and the perceived indifference of President Emmanuel Macron, whose government this week hardened its stance against them.

The street protests began peacefully in the French capital but degenerated later in the afternoon as protesters hurled missiles at riot police barricading bridges over the Seine river and torched garbage bins on the glitzy Boulevard Saint Germain.

According to police, 25,000 people took part in demonstrations across the country, of which 3,500 protesters in Paris. 18 people were also arrested.

A French minister said he had to be brought to safety after unknown persons broke through its main door using heavy machinery during protests in Paris.

"It's never very nice to see people using heavy machinery to smash their way into your workplace," minister and government spokesman Benjamin Griveaux told media.

But, he said, "I wasn't the one who was attacked. It was France, it was our institutions."

The attackers had used machinery they stole on the street outside, Griveaux said. Newspaper Le Parisien said sources had told it there had also been attempts to break into other ministries.

Despite a tense stand-off, the level of violence was far from the levels seen in early December when rioters ran amok in the city, torching dozens of cars, looting shops in posh neighbourhoods and defacing the Arc de Triomphe.

Officers fired tear gas to prevent hundreds of demonstrators crossing the river and reaching the National Assembly. One riverboat restaurant was set ablaze and a policeman wounded when he was struck by a bicycle hurled from a street above the riverbank.

Two months after they started blocking roads, occupying highway toll-booths and staging sometimes-violent street demonstrations in Paris, the yellow vests sought to inject new momentum into a movement that weakened over the holidays.

Shaken by the unrest, Macron's government began the new year on the offensive, branding the remaining protesters as agitators seeking to overthrow the government. Police on Wednesday night arrested one of the movement's prominent figures.

Driving the unrest is anger among workers and the lower-middle class over the squeeze on household incomes and a belief that Macron is deaf to citizens' needs as he enacts reforms seen as favouring the wealthy.

"They have no right to leave us in the s*** like this," said protester Francois Cordier. "We're fed up with having to pay out the whole time, we've had enough of this slavery, we should be able to live on our salaries."

There were also skirmishes between police and protesters in the northern port city of Caen. Thousands more rallied in Bordeaux in the southwest, Rouen in the north and Marseille in the southeast, though numbers appeared far below the turnout seen in early weeks of the protests.

"Power to the people"

The protests -- 18 months into Macron's tenure, and his drive to reshape the economy -- have already forced concessions from the 41-year-old president.

Last month, Macron promised tax cuts for pensioners, wage rises for the poorest workers and the scrapping of planned fuel tax increases to quell the unrest at a cost to the Treasury of 10 billion euros ($11 billion).

The measures marked the first big U-turn for a president elected 18 months earlier on a platform to break with traditional French politics and liberalise the heavily-regulated euro zone economy.

In a New Year's Eve address, Macron vowed to press on with his reform agenda, saying: "We can't work less, earn more, cut taxes and increase spending."

Faced with record low popularity ratings, Macron is expected to pen a letter soon to the nation setting out his plans for the coming months. These include a nationwide debate with citizens on ecological, fiscal and institutional questions, the results of which he says will feed into the policy-making process.

"We have to give power back to the people and not a minority that serves its own interests," said a second yellow vest protester outside the old stock market building.