A police officer in Paris was injured after being struck by a Molotov cocktail as clashes erupted in the capital and other cities during protests across France against soaring living costs and inequality.
Hundreds of thousands of people, some dressed for Halloween, demonstrated across France in a third consecutive weekend of largely peaceful demonstrations.
But the Paris police prefecture said that several hundred rioters had attacked security forces with projectiles, including a Molotov cocktail.
Interior minister Laurent Nunez pointed to an "extraordinary" level of violence from some, blaming far-left extremist groups for attacks on security forces.
He described the throwing of a Molotov cocktail at a riot police officer in Paris as an "attempted murder," adding that the officer had escaped with minor injuries.
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"We are fully prepared for those looking for confrontation tonight," he added.
After a march on the outskirts of Paris in bright sunshine, clashes broke out between police and some demonstrators as the procession reached its final destination.
Dozens of masked people dressed in black used hammers to pry up paving stones and hurl them at police, seen by journalists from the Agence France-Presse news agency. Police responded with tear gas and several baton charges.
Far-right leader Marine Le Pen said those responsible for the Molotov attack must be "punished with the utmost severity."
"The images of a police officer engulfed in flames after being targeted with incendiary devices are unbearable," Le Pen said on X.
A night-time curfew was to be imposed in the central Paris Republique and Chatelet-Les Halles neighbourhoods from 11pm to 6am on Saturday and Sunday local time.
Police arrested more than 420 people across the country.
The interior ministry said that "radical elements" in cities including Bordeaux, Toulouse and Marseille had attempted to enter city centres "with the aim of carrying out vandalism and looting".
In Lyon, France's third-largest city, people threw projectiles at police, prompting officers to fire tear gas.
In the southern city of Toulouse, police used water cannon against an unauthorised protest that drew several thousand people.
Earlier Saturday, thousands of people, some wearing costumes ranging from Spider-Man to Frankenstein, marched through eastern Paris as a helicopter circled overhead.
Placards read: "No need for tear gas to make our future look bleak" and "Dressed up as an angry citizen for Halloween."
"The fact that demonstrations are being pushed outside city centres, and that so many protests are being banned, is really an attack on freedom," said Alice Hien, a video game developer.
Authorities said that some 320,000 people rallied across France, including 70,000 in Paris.
According to youth organisations, nearly half a million people demonstrated, including 200,000 in the capital.
The demonstrations come in a febrile political climate, with presidential elections less than six months away and Le Pen topping opinion polls.
The protest movement, bringing together Yellow Vest activists, trade unions, and high school and university students, initially focused on the rising cost of living, inequality, and deteriorating learning conditions.
Following a security clampdown and serious injuries to some protesters, the movement broadened its demands to include greater protection of civil liberties and the right to protest.
In the northern French city of Lille, 47-year-old Aurelie Herrmann danced at the protest.
"I dance because on television they only show damage and destruction, whereas you can perfectly well demonstrate in good spirits," she said.
Student protesters complained the police had not authorised a march through the centre of the French capital and vowed to stage new blockades of high schools and universities next week.
"Starting this Tuesday, we will blockade our universities and high schools, and we will do so again on Thursday before joining the demonstration on November 5 called by workers and trade unions," said Sabrine Kharbach, spokeswoman for the Union Etudiante (Student Union).
Ahead of the protests, some shopkeepers barricaded their businesses.
With the eurozone's second-largest economy on the brink of recession and under pressure to rein in its debt, the government has limited scope to appease protesters through additional spending.
