PARIS (Reuters) – Hundreds of hooded protesters held up an annual May Day demonstration in eastern Paris on Tuesday, with some smashing the windows of a McDonald’s restaurant and hurling petrol bombs inside, Reuters television images showed.

French police warned on Monday of possible clashes with far-left anarchist groups, known as Black Blocs, after a call on social media for a “Revolutionary Day”.

Authorities said some 1,200 hooded and masked protesters had turned up on the sidelines of Tuesday’s planned demonstration by labor unions.

People hold a banner which reads, “Students, Employees. Everyone in the Street. General Strike” during the traditional May Day labour union march in Paris, France, May 1, 2018. REUTERS/Christian Hartmann

Images also showed the smashed windows of a Renault garage on a road near the Austerlitz station and a construction vehicle in flames.

The protesters moved towards riot police chanting anti-fascist slogans, waving Soviet flags and anti-government banners and throwing firecrackers. Some started to build barricades. The police used water cannon against some of the protesters.

President Emmanuel Macron, elected last May on a promise to shake up France’s creaking economy and spur jobs growth, is locked in a battle with the trade unions over his plans to liberalize labor regulations.

Railway staff have begun three months of nationwide rolling strikes in a dispute over the government’s planned overhaul of state-run railway SNCF.

(Reporting by John Irish; Editing by Gareth Jones)