The French city of Nantes has seen the return of the "yellow vest" protesters and looting, with police responding with tear gas and water cannon amid clashes.
Hundreds of demonstrators have faced police in a tense stand-off in the French city of Nantes as revived "yellow vest" protests against the government of President Emmanuel Macron took place across the country.
Police responded with tear gas after some protesters threw projectiles. A spokesman with the local prefecture said 21 people had been arrested.
Television footage on Saturday showed groups of black-clad protesters trying to break into shops while police trucks carrying water cannon were seen arriving on scene.
The Gilets Jaunes (yellow vest) protests, named after motorists' high-visibility jackets, began over fuel tax increases but morphed into a sometimes violent revolt against Macron and a government they see as out of touch.
The president has sought to ease tensions with 17 billion euros ($A28 billion) of countermeasures to boost the monthly minimum wage, remove some taxes, and offer relief to poor retirees. But he faces a new round of anger with a long-awaited reform that seeks to merge France's 42 different pension systems into a single points-based system.
Parisian commuters faced travel misery on Friday as metro workers went on strike over plans to reduce their retirement privileges.