Iranian security forces have clashed with opposition supporters in central Tehran, according to Jaras, an Iranian opposition website.
The confrontation comes as the Islamic Republic marks Ashura, a 10-day period of Shia religious ceremonies.
The report could not be independently confirmed, as foreign media have been banned from reporting directly on protests.
The same website earlier reported that hundreds of riot police were deployed in central Tehran.
“A large group of people and security forces clashed in the Pol-e Choubi area while people were marching,” Jaras said.
The reported clashes occurred as people around Iran marked the day of Tasoua with religious ceremonies which peak on Sunday, when Shia Muslims commemorate the 7th century death of Hossein, Prophet Muhammad’s grandson.
Six months after a disputed election plunged Iran into political turmoil, tension has again mounted after the death of Grand Ayatollah Hossein Ali Montazeri, a leading dissident religious leader, last week.
Mourning and burial ceremonies for Montazeri, who died aged 87, have sparked bloody confrontations with security forces.
Iranian police clashed on Thursday with Montazeri mourners, making arrests and injuring some, an opposition website said after Tehran warned of a crackdown.