Bordeaux town hall has been set on fire as French protests continued over plans to raise the pension age.
More than a million people took to the streets across France on Thursday, with 119,000 in Paris, according to figures from the interior ministry.
Police fired tear gas at protesters in the capital and 80 people were arrested across the country.
The demonstrations were sparked by legislation raising the retirement age by two years to 64.
Unions have called for further protests next Tuesday, which would coincide with King Charles III's state visit to the country.
He is scheduled to be in the southwest city of Bordeaux on that day, where fire engulfed the front door of the town hall on Thursday evening after a day of protests and clashes.
It was not clear who was responsible for the blaze, which was quickly put out by firefighters.
Interior Minister Gérald Darmanin sought to quell any concerns ahead of the King's trip, saying on Thursday night that security "poses no problem" and the monarch will be "welcomed and welcomed well", according to AP.
In Paris, generally peaceful demonstrations saw occasional clashes between police and masked rioters who smashed shop windows, demolished street furniture and attacked a McDonald's restaurant, according to Reuters news agency.
One police officer who lost consciousness was dragged to safety.
AP news agency reported that police forces used tear gas and were pelted by objects and fireworks, with 33 people arrested in the capital.
France's Prime Minister, Élisabeth Borne, tweeted: "Demonstrating and voicing disagreements is a right. The violence and degradation we have witnessed today is unacceptable. All my gratitude to the police and rescue forces mobilized."
"I oppose this reform and I really oppose the fact that democracy no longer means anything," a demonstrator told Reuters. "We're not being represented, and so we're fed up."
"It is by protesting that we will be able to make ourselves heard because all the other ways... have not allowed us to withdraw this reform," another told AFP news agency.
The unrest also disrupted train travel, oil refineries and saw teachers and workers at Paris's Charles de Gaulle Airport walk out of work.
Popular tourist attractions such as the Eiffel Tower and the Palace of Versailles, where a dinner is planned for King Charles and the French president next week, were also closed on Thursday.
In the northern city of Rouen a young woman was seen lying on the ground after sustaining a serious injury to her hand. Witnesses said she lost her thumb after she was hit by a so-called "flash-ball" grenade fired by police to disperse demonstrators.
There were other clashes in the western cities of Nantes, Rennes and Lorient.
"The street has a legitimacy in France," said a protester in Nantes. "If Mr Macron can't remember this historic reality, I don't know what he is doing here".
Unions and the political left have deemed the day a success, but where the situation goes from here is an open question.
The government is hoping that the protests will lose momentum, and that the violence on the streets will turn people away.
The opposition says that the protests will not dwindle, but unions will need to devise a strategy going forward, rather than promising more days like Thursday.
Since January, there have been nine days of protest and French unions have called for a tenth next Tuesday.
Parisian rubbish collectors, who started their strike against the pension reform on 6 March, have renewed it until next Monday.
The unrest followed the government's decision to force the legislation to raise the pension age through the lower house of parliament - where it lacks an absolute majority - without a vote.
French President Emmanuel Macron defended the move, saying the reform is a necessity.