Iranian riot police have clashed with protesters in the capital, Tehran, as opposition supporters gathered for anti-government protests on Iran's National Student Day.

Witnesses say hundreds of police used batons and tear gas to disperse demonstrators gathered in the streets of central Tehran.  Other police were reported to be blocking areas leading to Tehran University, where pro-reform students also are holding rallies.

National Student Day commemorates the killing of three Iranian students during an anti-American protest in 1953.

Reformist opposition activists were expected to turn the state-authorized event into a protest against the government of President Mahmoud Ahmadinejad.  

Since Sunday, Internet and cell phone services have been shut down or disrupted in areas where demonstrations were scheduled to take place.  

The government also has banned foreign journalists from covering news, revoking their work permits in Tehran from December 7 to December 9.

Former Iranian President Akbar Hashemi Rafsanjani on Sunday accused Iran's rulers of being intolerant, and of silencing any constructive criticism.

The powerful cleric also called on anti-government protesters to express their views "within the framework of law."

Iranian opposition leader Mir Hossein Mousavi said that students will not be silenced, despite pressure from the clerical establishment.

The reform movement has struggled to maintain momentum after the June presidential election sparked Iran's largest street protests since the 1979 Islamic Revolution.  Iranian security forces arrested thousands of activists, journalists and politicians during the unrest, and are accused of killing dozens of people.

VOA |Some information for this report was provided by AFP and Reuters.