French police clashed over the weekend with anti-government protesters seeking to inject fresh momentum into demonstrations calling for social justice and the ouster of President Emmanuel Macron. Protesters hope to galvanize support for a fresh wave of rallies across the country as the government begins a reform of France's retirement system.

In the French city of Nantes, police responded with tear gas after some protesters threw projectiles. A spokesman with the local prefecture said 21 people had been arrested.

Television footage showed groups of black-clad protesters trying to break into shops, while police trucks with water cannons were seen arriving on scene. Smaller rallies took place in other cities around France, including Paris, Marseille, Rouen, Lille, Strasbourg, Dijon, Bordeaux and Toulouse.

The yellow vest movement began last November, triggered by anger over a fuel tax increase. It quickly evolved into a broader movement against Macron, accused of ignoring the day-to-day struggles of low-income earners in small-town and rural France. The response of French President Emmanuel Macron's government to the yellow vest protests has been seen as an escalation of state violence toward its citizens as the U.N. recently urged a French probe into the use of force during the protests, in which more than 300 people were injured by police violence.