Hundreds of thousands of French youths took to the streets Thursday to protest a deeply unpopular new hiring law. The demonstrators clashed with riot police in the French capital.

What began as a massive but largely peaceful demonstration in Paris Thursday afternoon turned violent at the end of the day. Riot police fired rubber pellets and tear gas at youths, who hurled stones and set cars afire. Some of the clashes took place near the Sorbonne University, in the Latin Quarter -- one of the hubs of the current student unrest.

Altogether, police estimate roughly 250,000 people joined protests across France against the new first job contract law. The legislation allows employers to more easily hire -- and fire -- young workers during the first two years of their employment. The country's center-right government argues the law will help reduce youth unemployment in France, where roughly 23 percent of those under 26 years old are jobless. But many young French believe they will lose their job security under the new law.

But the law has sparked anger among students and other young people, who have poured into the French streets in recent days. The growing protests are shaping into the biggest crisis facing French Prime Minister Dominique de Villepin to date -- and threaten his potential bid to run in next year's presidential elections.

Those opposed to the job law include not only French youths, but also an array of labor unions and leftist opposition parties. But the protesters are not completely unified. For example, some young protesters, like Thomas, a university student in the French town of Poitiers, say they do not want the formal sponsorship of unions.

In an interview with France Info radio, Thomas said the unions suport the demonstrations in Poiters but they are not formally involved in them, and he wants it to stay that way.

Prime Minister de Villepin says he is open to dialogue, but that the new law will be applied. Still, a growing number of French appear to be opposed to it -- and not only the country's youth. A poll to be published Friday in France's Le Parisien daily, finds that 68 percent of those surveyed want the jobs law to be repealed.