TEHRAN, Iran - Riot police and hard-line vigilantes clashed with teenage demonstrators who denounced supreme leader Ayatollah Ali Khamenei Wednesday, as protests mushroomed into Iran's biggest in months.

Dozens of the hard-liners riding motorbikes chased down about 300 protesters, beating them with sticks in the streets outside a Tehran University dormitory. The protesters chanted "Death to Khamenei" and threw stones at police, who threw them back.

About 200 students in the dormitory compound threw stones and molotov cocktails at the police after officers joined the vigilantes in attacking the protesters. Several people were seen being carried away with head injuries.

The protests began peacefully Tuesday when a small student gathering against privatization of universities turned into the largest demonstration against Iran's political leadership since November. Then, students protested a death sentence imposed on Hashem Aghajari, a history professor at a Tehran teachers' college, who questioned the need to obey the Islamic clerics' every edict.

Police had arrested about 80 protesters before the clashes broke out. In Iran, criticism of Khamenei is punished by jail, and hard-liners say Khamenei's powers are unlimited and cannot be questioned.

Before the clashes broke out Wednesday, security officials warned that further demonstrations against the political leadership would not be tolerated.

"These people have been provoked by extremists inside the country and elements outside the country to chant illegal slogans," state-run television quoted Intelligence Minister Ali Yunesi as saying Wednesday.

He was apparently referring to satellite channels owned by Iranian opposition groups in exile that have encouraged Iranians to rise up against the ruling clerics. Although satellite dishes are officially banned, many Iranians still use them.

The protesters Tuesday night shouted harsh slogans against the political and religious leadership.

"The clerical regime is nearing its end!" the demonstrators chanted. "Vigilantes commit crimes, the leader supports them."

In a rare twist, demonstrators also called for the resignation of Mohammad Khatami, the popularly elected reformist president, accusing him of not introducing enough reforms.

An Intelligence Ministry official, speaking to The Associated Press on condition of anonymity, said the people were arrested for chanting slogans against the ruling political leadership and for participating in unauthorized demonstrations.

The identities of the detainees have not been clearly established, the official said, but most of them did not appear to be students.

The arrests may have also been a warning before July 9, when students plan to commemorate the day four years ago when hard-liners and security forces attacked students protesting media restrictions. At least one student was killed and the clash touched off the worst street battles since the 1979 revolution that ousted the U.S.-backed shah.