Iranian security forces using batons and tear gas stormed anti-government marches in Teheran on Wednesday during state-sanctioned rallies marking the 30th anniversary of the takeover of the US Embassy, witnesses and state media reported. Witnesses told The Associated Press that security forces - mainly paramilitary units from the Revolutionary Guard - swept through an opposition march in central Teheran, 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 (one kilometer) from the annual anti-American gathering outside the former US Embassy. The witnesses spoke on condition of anonymity because of fear of reprisals from authorities. Media restrictions imposed after the disputed presidential elections in June limit journalists to covering state media and government-approved events, such as the rally outside the former US Embassy. Watch footage of today's protests: The state-run Islamic Republic News Agency reported that police used tear gas in other parts of the city to disperse protesters, making their first major show of force on the streets since September. 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 Teheran 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 - a familiar sight during the unrest following President Mahmoud Ahmadinejad's re-election in June. Many marchers Wednesday wore green scarves or wristbands that symbolized the campaign of Mir Housein Mousavi, who claims Ahmadinejad stole the election through vote fraud. Mousavi 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. Hundreds were seen in Haf-e-Tir Square, some chanting "Death to the Dictator." Other witnesses - also speaking on condition of anonymity - said about 2,000 students at Teheran University faced off against security forces, but there were no immediate reports of violence. The clashes and confrontations marked the first significant public display of opposition unity since marches in late September that coincided with state-sponsored protests against Israel. Authorities appeared determined to avoid opposition rallies overshadowing the 30th anniversary of the embassy takeover. Thousands of people gathered outside the former embassy, waving anti-American banners and signs praising the Islamic Revolution. The main speaker, hard-line lawmaker Gholam Ali Haddad Adel, denounced the United States as the main enemy of Iran. He did not mention the talks with the West, including the United States, on Iran's nuclear program.