Vigilantes on motorcycles chased down protesters and beat them with cattle prods Friday as anti-government demonstrations in Tehran (search) exploded in street battles.
In some parts of Tehran, pro-government thugs circled knots of student protesters, gunning their motorcycle engines. Some of the demonstrators fought back, punching the attackers and setting their motorcycles on fire.
At times, riot police prevented the vigilantes from confronting the students. Other times, police rushed the protesters themselves, sending them fleeing into the darkness.
The violence subsided by daybreak.
It was the third night of demonstrations against Iran's hard-line clerics, who are locked in a power struggle with reformist President Mohammad Khatami (search). Hundreds of young Iranians, many in their teens, have taken to the streets around Tehran University and the Intercontinental Hotel to denounce the country's supreme leader, hard-liner Ayatollah Ali Khamenei (search).
"Khamenei, the traitor, must be hanged!" they chanted. Criticism of Khamenei is usally punished by imprisonment, and public calls for his death had been unheard of until this week.
The pro-Khamenei vigilantes responded with chants of "Oh, exalted leader, we are ready to follow your instructions!"
Thousands of people looked on, sometimes clapping with the protesters and taking up their chants. Residents near the university hospital left their doors open so that demonstrators could find quick shelter if the authorities moved in.
Traffic was bumper-to-bumper in downtown Tehran until the early hours of the morning as curious residents stayed out to watch developments.
Khamenei warned of a major crackdown in a speech broadcast on state television and radio Thursday.
He referred to violence in 1999, when security forces and extremist supporters of hard-line clerics attacked pro-democracy demonstrators after a student hostel was stormed. The raid on the hostel led to the death of at least one student and generated the worst street battles since the 1979 Islamic Revolution.
"If the Iranian nation decides to deal with the (current) rioters, it will do so in the way it dealt with it on July 14, 1999," Khamenei said.
"It should not be allowed that a group of people contaminate society and universities with riots and insecurity, and then attribute it to the pious youth," he said.
Some protesters have vowed to continue demonstrating until next month's anniversary of the 1999 protests.
Reformist newspapers, which reflect the thinking of liberal politicians who have been fighting for change, offered little commentary on the unrest.
Exiled opposition groups have been encouraging dissent in Iran through U.S.-based Persian language TV channels. U.S. pressure on Iran, which Washington accuses of hiding a nuclear weapons program and harboring terrorists, may have further emboldened those who hope to see the regime toppled.
This week's demonstrators have also called for the resignation of President Khatami, accusing him of not pushing hard enough for democratic reforms.
Khatami does not have the support of the hard-liners who control the judiciary, the security forces and other unelected bodies. But the hard-liners do not enjoy popular support, leaving the two sides of government in a stalemate.