TEHRAN, Iran - Iranian security forces fired on stone-throwing protesters in the center of the capital yesterday in one of the bloodiest confrontations in months, opposition Web sites and witnesses said. At least five people were killed.
Some accounts of the violence in Tehran were vivid and detailed, but could not be independently confirmed because of government restrictions on media coverage.
Police, who denied using firearms, said that dozens of officers were injured and more than 300 protesters were arrested.
The dead included a nephew of opposition leader Mir Hossein Mousavi, according to Mousavi's Web site, Kaleme.ir.
The clashes were sure to deepen antagonism between the government and a reform movement that has shown resilience in the face of repeated crackdowns.
The street chaos coincided with commemorations of Shiite Islam's most important observance, Ashoura, fueling protesters' defiance with its message of sacrifice and dignity in the face of coercion.
Still, many demonstrators had not anticipated such harsh tactics by the authorities, despite police warnings of tougher action against any protests on the sacred day.
Amateur video footage purportedly from the center of Tehran showed an enraged crowd carrying away one casualty, chanting, "I'll kill, I'll kill the one who killed my brother."
In several locations, demonstrators confronted security forces, hurling stones and setting their motorcycles, cars and vans ablaze, according to video footage and pro-reform Web sites.
Protesters tried to cut off roads with burning barricades. One police officer was photographed with blood streaming down his face after he was set upon by the crowd.
There were unconfirmed reports that four people died in protests in Tabriz in northwest Iran, the pro-reform Rah-e-Sabz Web site said.
Fierce clashes also broke out in Isfahan and Najafabad in central Iran and Shiraz in the south, it said.
Mousavi's Web site said that the nephew, Ali Mousavi, was shot in the back on Azadi Street, or Freedom Street, during clashes in which security forces reportedly fired on demonstrators, and was taken to Ibn Sina Hospital. It said that Mousavi and other family members rushed to the hospital.
A close aide to Mousavi, a presidential contender in a disputed June election, said that Ali Mousavi died of injuries in the hospital. The aide spoke on condition of anonymity because of fears of reprisals from the government.
The protests began with thousands of opposition supporters chanting "Death to the dictator," a reference to hard-line President Mahmoud Ahmadinejad, as they marched in defiance of official warnings of a harsh crackdown. Ashoura commemorates the seventh-century death in battle of one of Shiite Islam's most beloved saints.