Venezuelan police have used water cannon and rubber bullets to break up a protest against a law that increases government control over universities.
Dozens of police and national guard troops blocked a march by students outside the Central University of Venezuela in Caracas.
The protesters say the new law will be used to promote President Hugo Chavez's socialist ideology in universities.
The government says it is designed to make them more democratic.
Hundreds of students gathered at the university to begin a protest march after the law was passed early on Thursday morning.
But riot police stopped them from leaving the university grounds and marching on the parliament building, saying the demonstration had not been authorised.
At least three people were injured during the clashes, including an opposition politician and a news agency photographer.
Student leaders say the law on university education damages the autonomy of Venezuela's state universities, which have been a bastion of anti-government protests.
The new law "imposes socialism as the sole ideology and does away with university autonomy because it concentrates all powers in the minister for higher education", the university's student federation leader, Diego Scharifker, told the Associated Press news agency.
The government says the law makes universities more democratic by giving university workers, as well as students and teachers, a say in how they are run.
One university worker, Carlos Lopez, said the law would break the control of education by Venezuela's "oligarchy" and make universities truly autonomous.
"With this law we begin a new stage of education in Venezuela, where all education is democratised," he told Venezuelan National Radio.
The higher education law is the latest in a series of measures passed in the final days of the current parliament, which is dominated by Mr Chavez's supporters.
A new National Assembly, with many more opposition members, will be sworn in on 5 January.
The opposition has accused Mr Chavez of rushing laws through to increase his hold on power and avoid proper parliamentary scrutiny.
Last week the assembly gave Mr Chavez special powers to pass laws by decree for 18 months to deal with the aftermath of devastating floods.