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PARIS — French security forces fired tear gas and flash-bang ammunition at protesters during a march through picturesque central Paris on Saturday as several thousand supporters of the "yellow vest" movement kept up pressure on President Emmanuel Macron with the first action of 2019.

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.

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The march on the eighth consecutive Saturday of "yellow vest" protests had been declared in advance and approved, in contrast to some illegal December demonstrations that degenerated into vandalism, looting and chaos.

The atmosphere mostly was calm, 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.

Some confrontations between police and protesters took place in other cities around France, with tear gas fired in Bordeaux in the southwest and in Rouen in Normandy.

No official figures have been issued for the number of protesters who turned out around France or in Paris. BFMTV, quoting several police sources, estimated the number of protesters in the French capital in mid-afternoon at 3,500.

Protesters were looking to breathe new life into the "yellow vest" movement as numbers of participants fell since the first Saturday protest in mid-November. They reiterated their call for Macron, denounced as the president of the rich, to resign.

Authorities have warned that they would not tolerate illegal acts. One known figure in the movement, Eric Drouet, was detained overnight this week for allegedly organizing an illegal demonstration, his second arrest. On Friday, government spokesman Benjamin Griveaux said those still protesting "want insurrection."

Thousand of "yellow vest" protesters walk alongside the Seine in Paris on Jan. 5, 2019. Ian Langsdon / EPA

He called on the French to express their views during a "national debate" organized in the coming weeks in all regions, rather than by taking to the streets.

The "yellow vest" movement was launched to express anger over fuel tax hikes hurting working people who commute by car, but grew to encompass broader anger over Macron's economic policies, deemed to favor the rich. It's named after the fluorescent protective gear French motorists must keep in their cars.