PARIS (AP) — French security forces fired tear gas and flash-balls after a march through picturesque central Paris went from peaceful to provocative Saturday as several thousand protesters staged the yellow vest movement's first action of 2019 to keep up pressure on President Emmanuel Macron.

A river boat restaurant moored below the clashes on the Left Bank of the Seine River caught fire. Smoke and tear gas wafted above the Orsay Museum and the gold dome of the French Academy as riot police, nearly invisible at the start of the demonstration, moved front and center when protesters deviated from an officially approved path.

Police boats patrolled the river while beyond the Seine, motorcycles and a car were set on fire on the Boulevard Saint Germain, a main Left Bank thoroughfare. Riot police and firefighters moved in, and barricades mounted in the middle of the wide street also glowed in orange flames.

Protesters made their way to the Champs-Elysees Avenue, the famed boulevard that has been at the center of previous yellow vest demonstrations, many removing their distinctive vests and mixing with shoppers.

Riot police moved in with a water cannon to evacuate the avenue. A line of parked cars burned on a nearby street.

In a first, the building housing the office of the French government spokesman was attacked. Government spokesman Benjamin Griveaux was evacuated from his Left Bank office at the Ministry for Parliamentary Relations after the front door of the building was partially destroyed.

"It wasn't me who was attacked ... It was the institutions, the democratic form of government," Griveaux said later, explaining on French TV that he and a half-dozen colleagues were taken out a back door while a group attacked the front door with construction equipment.

Those who did this "attacked the house of France," he said.

It was the first such attack on government property since the yellow vest movement began weekly protests eight Saturdays ago, in mid-November. Protesters have tried to reach the presidential Elysee Palace, which is protected like a bunker.

Saturday's march had been declared in advance and approved, in contrast to some illegal December demonstrations that degenerated into vandalism, looting and chaos.

The latest demonstration was a sort of test of the movement's staying power after proposals by Macron to address concerns of the French who have a hard time making ends meet, including canceling the fuel tax hikes at the origin of the protests.

Interior Minister Christophe Castaner estimated that about 50,000 people participated in protests around France on Saturday. Police counted some 3,500 protesters in Paris.

The atmosphere was initially calm in the French capital, but turned when some protesters tried to cross the river on a pedestrian bridge not on the official route from City Hall to the National Assembly, the lower house of parliament. Police used clubs and tear gas, then held the bridge in a standoff while violence broke out.

Video on French TV showed a man repeatedly stomping on an officer in riot gear on the ground and hitting the shield of another officer.

Some confrontations took place in other cities around France, with tear gas fired in Bordeaux and in Rouen in Normandy.

Protesters were looking to breathe new life into the yellow vest movement, named after the fluorescent protective gear French motorists must keep in their cars. The protests were launched in anger over fuel tax hikes, but have swelled with broader anger over Macron's economic policies, deemed to favor the rich.

On Saturday, protesters reiterated a call for Macron to resign.

"Resolution 2019: Demacronize," read one sign. "Power to the people," read another.

Government spokesman Griveaux had said on Friday that those who show up to protest "want insurrection" as the movement appears to wane and radicalize.

He called on the French people to express their views during an upcoming "national debate" rather than by taking to the streets.