Hundreds of thousands of people are demonstrating across France against the government's controversial new youth employment laws.
Fighting broke out as protesters gathered in Paris,
and missiles were hurled at police as they moved into the crowds to try to remove troublemakers.
The BBC's Jon Sopel in Paris said the protest was initially mainly peaceful, but the mood had deteriorated.
A nationwide strike has also caused travel chaos throughout the country.
As the trouble erupted in the Place de la Republique in Paris, our correspondent said his BBC crew had also come under attack, although he added the violence had remained "low-level" so far.
Extra riot police were deployed before the march, after a rally in Paris last week led to running battles.
French Interior Minister Nicolas Sarkozy told them to only get tough with those he called delinquents.
"My first instruction is that you protect the demonstrators, especially the youngest ones," he said.
"The second instruction is to arrest as many thugs, that means delinquents, as you can."