The car of the Iranian opposition leader Mirhossein Mousavi was attacked by men on motorbikes as he was returning to Tehran from the funeral of a leading dissident cleric.
The reformist Kaleme website reports that one member of Mr Mousavi's entourage was injured when the assailants shattered the car's back window.
Mr Mousavi was in the holy city of Qom for the funeral of the Grand Ayatollah Hossein Ali Montazeri, who was one of the leading critics of the Iranian government.
The website also says the police and security forces clashed with a group of chanting mourners gathered in front of the cleric's house after the funeral, which turned into a massive anti-government rally.
Thousands of mourners poured onto the streets of Qom, many of them chanting slogans and displaying the green of Iran's opposition.
Ayatollah called election result a fraud
The ayatollah, who died on Saturday aged 87, was one of the leaders of the 1979 Islamic revolution and, more recently, a strong critic of the government. At one stage, the BBC reports, he was set to become the nation's spiritual leader.
He was also a leading critic of President Mahmoud Ahmadinejad. He issued a fatwa condemning Mr Ahmadinejad's government after June's disputed election, which he described as a fraud
The Iranian authorities banned foreign media from covering his funeral, fearing it would become a rallying point for the opposition.