French police have fired tear gas on masked protesters who joined large May Day demonstrations in Paris, reports BBC.
Traditionally a union-led day of action in the country, this year's event saw both the yellow vest movement and so-called "black blocks" of dark-clad and masked protesters.
Some smashed shop windows and threw projectiles at the police. Dozens of people have been arrested.
The clashes forced the head of the CGT union to temporarily flee the march.
Philippe Martinez told news outlet Franceinfo that "police charged the CGT", though other witnesses had said the "black blocks" had attacked the union march.
AFP news agency says Mr Martinez planned to return.
Police issued a statement saying the union was never targeted, but that police "have carried out their mission with determination against violent thugs".
French broadcaster BFMTV reports that the clashes forced the teachers' union FSU to leave the event.
By early afternoon, France's interior ministry said more than 150,000 demonstrators had taken to the streets around the country, and at least 16,000 in the capital - a significant increase on last year's estimates.
Another estimate from media groups put the number far higher, at some 40,000 in Paris.
More than 200 arrests have been made in the capital.