Police surround Tehran university protesters

Thousands of riot police and Revolutionary Guard members armed with tear gas, batons and firearms were deployed outside Tehran University today to prevent student demonstrations backed by the opposition.

The large security operation suggested that authorities planned to make good on their promise to deal harshly with protesters marking the day in 1953 when three students were killed in an anti-US protest. The occasion has in recent years been used by students to stage pro-reform demonstrations.

There was no word immediately available on whether demonstrations have begun inside the campus, but the witnesses said police were conducting ID checks on anyone entering the campus to prevent opposition activists from joining the students.

Journalists working for foreign media organisations are banned from covering today's planned protests. They were told on Saturday by the Culture Ministry that their press cards would be suspended for three days starting today.

Last night, government opponents braved pouring rain to climb onto Tehran rooftops and shout "Allahu Akbar" and "Death to the Dictator."

The protest reprised one of the main tactics of the anti-shah movement in the 1979 Islamic Revolution and was revived in the days and weeks after the disputed elections.

The rooftop chants had not been heard since the opposition's last attempt to mobilise a rally last month coinciding with state-sanctioned events to mark the anniversary of the 1979 US Embassy takeover. That demonstration drew far fewer protesters than at the height of the summer's unrest. But it still provoked a violent response from security forces.

Authorities have also choked off internet access to deny the opposition a vital means of communication used in the past to mobilise supporters.

Government opponents were hoping for a large turnout for today's demonstrations to show their movement still has momentum despite a series of government crackdowns since the country's disputed presidential election in June.

Opposition leader Mir Hossein Mousavi threw his support behind the planned student demonstrations and declared that his movement was still alive. A statement posted on his website said the clerical establishment cannot silence students and was losing legitimacy in the Iranian people's minds.

"A great nation would not stay silent when some confiscate its vote," said Mousavi, who claims President Mahmoud Ahmadinejad stole the June 12 election victory from him by fraud.

Supreme Leader Ayatollah Ali Khamenei, who has the final say on all state matters, accused the opposition of exposing divisions in the country and creating opportunities for Iran's enemies.

Iran's universities have been strongholds of the opposition movement that grew out of the disputed June election, and authorities have besieged campuses nationwide with a wave of arrests and student expulsions.

The pro-government Basij militia has also recruited informers on campuses to blow the whistle on any opposition troublemakers, according to students.