Four demonstrators and 15 police were hurt, including two officers who sustained burns due to Molotov cocktails, as tens of thousands rallied against the law forced through by the Socialist government.
Police used water cannon and tear gas as protests also turned violent in Nantes in western France, one of at least 10 provincial cities which saw rallies.
"The violence is unacceptable," said Interior Minister Bernard Cazeneuve, noting that police had arrested 62 people across the country, 32 of whom were kept in custody.
The law aimed at loosening France's notoriously rigid employment laws was forced through in July after months of often violent protests. In all 620 police have been injured since the protests started, said Cazeneuve.
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It notably makes it easier to fire workers during downturns and for bosses to negotiate directly with employees on working time.
As well as the protests, scores of flights in and out of the country were also cancelled as air traffic controllers went on strike to protest the law.
Turnout nationwide was far lower than at the first rallies earlier this year which saw hundreds of thousands of people take to the streets.
One of the focal points today was the eastern city of Belfort, where the government is locked in a battle with train-building giant Alstom over the future of a locomotive factory threatened with closure.
Hundreds of demonstrators marched through the city, chanting "Alstom is Belfort, Belfort is Alstom".
Last week, Alstom had announced it would close the plant due to a lack of orders and move production to a site 200 kilometres to the north.
The prospect of up to 400 job losses is deeply embarrassing for the Socialist government eight months ahead of presidential and parliamentary elections, in which high unemployment is expected to be a key issue.
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