French riot police have grappled with protesters at the Sorbonne in Paris in unrest over a new labour law, making it easier to sack young employees.
Police stormed the university early on Saturday to drive out at least 150 people, mainly students, some of whom had been inside for three days.
They used tear gas and batons to clear the main building in under 10 minutes, correspondents report.
At least two people were injured and some arrests were made.
About 40 of France's 84 universities saw student occupations to varying degrees on Friday in protest at the new law, according to French news agency AFP.
Interior Minister Nicolas Sarkozy has cut short a visit to France's Caribbean Antilles Islands because of the student unrest, his entourage said.
The First Employment Contract (CPE) passed by parliament on Thursday is a two-year contract for under-26-year-olds which employers can break off at any time without explanation.
Ministers hope the flexibility will encourage employers to hire more young people, safe in the knowledge that they will be able to get rid of them if they have to.
Critics say younger workers would have less job security than older colleagues and France's generous labour provisions would be undermined.
The new legislation currently only applies to small firms but some fear it could be misused by larger employers and make it even harder for young people to find a permanent job.
Extinguishers and books
Nicolas Boudot, a local educational authority administrator, said about 300 people had entered the Sorbonne on Friday by breaking windows and not all of them were students.
Students at Nantes University are among those on strike
The protesters, he said, were trying to turn the Sorbonne into a battlefield for fighting social woes.
Other students had been inside the building since Wednesday as part of the students' strike.
Riot police in the square outside the university fired tear gas shortly after midnight (2330 GMT Friday) after being pelted with objects including fire extinguishers from upper-storey windows of the university.
The police moved in to pull away a barricade from the main doors, all the while under a hail of projectiles.
After withdrawing, about 80 officers returned just before 0400 (0300 GMT), apparently getting into the main building by a back door before driving out the protesters.
The police reportedly acted on a request from the educational authorities.
Police also used batons on students at a road-block near the university on Friday.
Protesters had marched around the building shouting "The Sorbonne belongs to students!"
The Mayor of Paris, Bertrand Delanoe, has said he is "deeply concerned" about the use of force by police against the protest, which he said had been passing off peacefully.
At least 100,000 people protested in cities across France on Tuesday against the new law, disrupting airports and public services.
The overnight violence has echoes of the labour and student unrest of 1968 in Paris.
One Parisian student, named only as Elodie, told AFP it was not a conscious attempt to repeat those riots.
"The context is different," she said. "In '68, the students when they left university, they found work."