At the march's terminus in the Place de la Republique in the northeast of the capital, gangs of youths flung taunts and projectiles at riot-police who responded with baton-charges and tear-gas.

Police arrested more than 500 trouble-makers on the sidelines of the march in Paris, and across the country more than 800 arrests were made after violent incidents in cities including Marseille, Rennes and Grenoble.

Some 60 people were injured in the strikes, including nine police officers, according to police reports.

Unions vow to continue

The scale of the protests was one of the biggest in modern French history, and unions -- who put the figure of participants between two and three million -- claimed another success in their escalating campaign against the First Employment Contract (CPE).

"It is historic," said Bernard Thibault of the CGT union. "It is unthinkable for the prime minister to stay fixed in his position. For us there is just one outcome and that is withdrawal of this reform."

Francois Chereque of the CFDT union was a bit more skeptical.

"I do not know if today's mobilization will make the prime minister give way," he said. "But what I do know is that each week we will be out in greater numbers."

Joining the demonstrating students were transport workers, teachers and other government workers closed schools, slowed mass transit and disrupted public services.

Police had deployed in large numbers to avoid a repeat of last Thursday's violence, when youths, mainly from high-immigration city suburbs, set fire to cars and mugged demonstrators.

Villepin stands firm

Meanwhile unions turned down an invitation from French Premier Dominique de Villepin to attend new talks on the contested contract, which was voted through parliament two weeks ago and is awaiting approval by constitutional experts before passing into law.

Opponents are demanding withdrawal of the CPE, but the prime minister is offering only "adjustments" on its two most contentious aspects: a two-year trial period, and the free hand given to employers during that period to sack under 26-year-olds without explanation.

Villepin told the National Assembly that he regretted the union's refusal to enter talks.

"As I have said, I am ready to engage in dialogue and adjust the contract on these two points," he said. "I said that in writing to the unions, but they refused my extended hand."

The government insists the contract is vital to fighting youth unemployment, which can reach more than 50 percent in the poor suburbs hit by last year's riots, but opponents say it is a breach of hard-won labor rights.

Sarkozy urges compromise

President Jacques Chirac, who has so far given his backing to Villepin, cancelled a visit this week to the northern port of Le Havre in order to stay close to the events in Paris.

But there were signs of dissension within the ruling Union for a Popular Movement (UMP), whose president, Interior Minister Nicolas Sarkozy, was quoted by deputies as urging Villepin to give ground.

An Ipsos poll for Le Monde newspaper gave some comfort to Villepin, who has staked his political career -- and presidential ambitions -- on getting the CPE into law.

While 63 percent of the population disapproved of his decision to stand by the CPE, views were heavily influenced by political allegiance. Some 74 percent of voters for his Union for a Popular Movement (UMP) supported his position.