Iranian security forces using batons and tear gas stormed anti-government marches in Tehran on Wednesday during state-sanctioned rallies marking the 30th anniversary of the takeover of the US Embassy, witnesses and state media reported.

Witnesses said that security forces — mainly paramilitary units from the Revolutionary Guards — swept through an opposition march in central Tehran, clubbing some protesters and kicking and slapping others.

There were no immediate reports on injuries or arrests in the clashes in Haf-e-Tir Square — about a half-mile from the annual anti-American gathering outside the former US Embassy.

The state-run Islamic Republic News Agency reported that police used tear gas in other parts of the city to disperse protesters.

Iranian authorities had warned protesters against attempts to disrupt or overshadow the annual gathering outside the former US Embassy, which was stormed by militants in 1979 in the turbulent months after the Islamic Revolution. A total of 52 Americans were held hostage for 444 days.

Security forces fanned out around Tehran at daybreak on Wednesday after opposition leaders refused to call off their appeals for counter protests.

Volunteer militiamen linked to the Revolutionary Guard patrolled the streets on motorcycles.

Many marchers wore green scarves that symbolised the campaign of Mir Hussein Moussavi. Moussavi and his allies, including former President Mohammad Khatami, appeared to encourage opposition protesters to return to the streets.

The full extent of the opposition marches was not immediately clear. Some witnesses said about 2,000 students at Tehran University faced off against security forces, but there were no immediate reports of violence.