Iranian police and Islamic vigilantes beat demonstrating students with batons and lobbed tear gas canisters today to impose control around Tehran University after five days of student protests.

The police and vigilante attacks started in the streets against marching students, who hurried to barricade themselves inside the university and burned tires at the gates. It was unclear if the police and vigilantes had stormed the campus itself, where students have been staging rallies to protest an attack last week on a peaceful demonstration in support of press freedom.

The protests have provoked a crisis that has shaken Iran and put pressure on President Mohammed Khatemi to accelerate his promised reforms despite resistance from the powerful clerical establishment.

Today's crackdown followed a stern warning Sunday by Iran's top security body against holding unauthorized demonstrations, reinforced by a new edict from authorities today banning any protests Tuesday.

Vigilantes and police patrolled streets near the university. But after the initial clashes, police apparently allowed most students to leave, and ambulances evacuated an estimated 50 injured people. At least one bus was burning outside the campus. Inside the campus, medical students were seen trying to treat the injured at the campus mosque.

"We were attacked by police with batons as they tried to disperse students," said one of the wounded at the mosque. "Our brothers fled into the side streets, and from there they were attacked by an orchestrated action of riot squads in complete coordination with the Ansar Hezbollah."

Ansar Hezbollah, a youth auxiliary of conservative Islamic groups, has been opposing the student demonstrators and acting as vigilante squads in street clashes. It was not immediately clear if any students were arrested in the latest crackdown.

Club-wielding police clashed earlier today with several hundred students in a square several miles from the campus. Witnesses said many people were injured and shop windows were smashed.

Khatemi, who chairs the Supreme National Security Council, called for a peaceful end to the rallies.

"The bulk of the students have shown restraint and prevented [the rallies] from turning into a difficult national question. . . . Now, students should cooperate with the government and allow law and order to be established," Khatemi said in a meeting with education officials.

But the Tehran students vowed to keep up their protests until their demands are met. These include designating a national day of mourning for students killed, an open trial for the police officers who ordered and carried out last week's attack on a dormitory and the handing over of the bodies of those killed.