STORY: In central Paris, where demonstrators were generally peaceful, smaller groups of "Black Bloc" anarchists smashed shop windows, demolished street furniture and ransacked a McDonalds restaurant. Clashes ensued as riot police moved in and drove back the anarchists with tear gas and stun grenades.

BFM TV quoted police as saying 21 people were arrested.

Labour unions fear that protests could turn more violent if the government does not take the growing popular anger over the pension curbs into consideration.

Macron broke weeks of silence on Wednesday on the new policy to say he would stand firm and the law would come into force by the end of the year. He compared protests to the Jan. 6, 2021 storming of the U.S. Capitol.