TEHRAN, Iran - Several thousand protesters took to the streets of Tehran yesterday and clashed with security forces in the latest round of unrest over Iran's disputed June presidential elections, according to witnesses and amateur video posted online.

The protests come as Iran steels itself for a potential outbreak of violence this weekend during Ashoura, the annual commemoration of the seventh-century martyrdom of Imam Hussein, grandson of the prophet Muhammad and a revered figure in Iran's Shiite Muslim faith.

The death last Saturday of Iran's leading dissident cleric, Ayatollah Hossein Ali Montazeri, has added to the politically charged atmosphere. Iranian authorities have banned all mourning commemorations for him, as the religiously significant seventh day of mourning coincides with Ashoura, when men traditionally pour into the streets.

Protesters yesterday gathered at Imam Khomeini Square in central Tehran as police in full riot gear circled. Demonstrators chanting "Death to the dictator" played cat-and-mouse with police into early evening. The fleeing crowd took refuge in the stairs of the nearby subway station as passing motorists leaned on their horns in gestures of support.

"Montazeri's legacy is the end of this dictatorship," the protesters chanted.

Clashes also took place between security forces and mourners trying to honor Montazeri in Zanjan, a mostly ethnic Azeri city of 375,000 in western Iran, several opposition Web sites reported.

Amateur video posted to the Internet showed Montazeri supporters in Zanjan holding up pictures of him and chanting, "God is great."

Iranian authorities have called the opposition movement a tool of foreign powers trying to weaken the Islamic Republic. Supreme Leader Ayatollah Ali Khamenei and his deputies have repeatedly called on protesters to leave the election in the past, to little avail.

Yesterday, supporters of opposition figures Mir Hossein Mousavi and Mehdi Karroubi, who lost to President Mahmoud Ahmadinejad in June's disputed elections, released a 370-page report detailing alleged voting fraud.

Iranian authorities maintain that Ahmadinejad's opponents failed to prove any significant cheating in the elections. Ahmadinejad described Iran to ABC News this week as a paragon of civil liberties.