French President Francois Hollande vowed to stick with his controversial attempts to reform the labour market, even as a new round of violent protests broke out.
Police fired tear gas in central Paris as an initially peaceful protest organised by unions and students was disrupted by a more radical fringe.
The labour reforms have sparked two months of protests on France's streets, drawing 68,000 nationwide on Tuesday, authorities said, while organisers put the turnout at 220,000.
"Withdraw, withdraw this law of the wealthy, it's the law of the bosses," was the message blasted from loudspeakers at the Paris march.
But Hollande said the battle against unemployment was not yet won and he placed the need to reform over his personal popularity, which remains at near-record lows a year ahead of a possible bid for re-election.
"I will not give way, because too many (previous) governments have backed down," Hollande said in an hour-long interview with Europe 1 radio.
"I prefer that people have an image of a president who made reforms rather than a president who did nothing," he said.
Police were quick to act as violence by masked youths broke out during the march in central Paris, kicking off another week of nationwide strikes and demonstrations against the package of reforms. Some 87 people were arrested.
Demonstrations were also reported in cities across the country from Marseille in the south to central Lyon and Lille in the north.
Lorry drivers blocked roads and ports in northern and western France, and there were clashes between protesters and police in the western cities of Nantes and Rennes, where thousands more took to the streets.
We have been ignored, so we will work even harder to make our voices heard," said Philippe Martinez, head of the CGT union, at the Paris rally.
The government argues the changes contained in the draft law will make France's notoriously rigid labour market more flexible, but opponents say it will erode job security and do little to bring down the unemployment rate, stuck at 10 percent and nearly 25 percent for young people.
The labour reform, which would make it easier for employers to hire and fire workers, is likely the last major piece of legislation for Hollande, the least popular leader in modern French history who faces a re-election next May.
- 'No alternative' -
Hollande has pledged to decide by the end of this year whether to run for a second term, but he said Tuesday he saw "no alternative" to himself on the left of French politics.
"If I am not there... if the left is not re-elected, the right or the extreme-right will win," he said.
Hollande is staking his bid on bringing down the jobless rate.
"It takes time for those reforms to take effect," he said.
"The battle is not won. It will only be won when we have, over several months, a sustained fall in unemployment," he said. "I am fighting the battle every day."
The Socialist government last week survived a vote of no-confidence, called by the centre-right opposition, after it forced through the labour market reform bill without parliament's approval.
The draft law will now be debated in the Senate, the upper house of parliament.
A defiant Hollande said the draft law "is going to go through because it has been debated, agreed on and amended".
- Transport strikes -
The president also promised tougher action against troublemakers who infiltrate street protests against the reforms and provoke confrontations with the police.
Hollande said more than 1,000 people had already been arrested and that 350 police officers had been injured in the violence.
A police demonstration was set for Wednesday to protest "anti-cop hatred" in the months of clashes over the labour reforms.
Police unions called on officers not on duty to gather in some 60 locations across France, including the Place de la Republique in Paris.
Despite the clashes over labour reform, 82 percent of the French have a positive opinion of the police, according to an Odoxa survey.
Major travel disruption is expected through the week, with rail unions holding several strikes and airport unions planning a walk-out on Thursday that will see some 15 percent of flights cancelled at Paris Orly airport, the capital's second largest.
Ports are again due to be blocked on Thursday, and rail unions said strikes would resume at the end of the month.