Iranian police and security forces on Thursday broke up a demonstration by mourners remembering those killed in recent post-election clashes, and prevented Mir Hussein Moussavi from attending, witnesses said.
Police used batons to break up a crowd of several hundred who had gathered around the grave of Neda Agha-Soltan, who died during last month's protests against the re-election of President Mahmoud Ahmadinejad. Witnesses said there were a number of arrests.
Neda Agha-Soltan was shot on an open street in Tehran June 20, and her death became symbolic of the protest movement in Iran and also prompted a wave of international protest after internet images of the 27-year-old's death were shown around the world.
Witnesses said Moussavi was prevented from getting out of his car when it arrived at the scene of the mourning, which in the Shiite Muslim tradition went ahead 40 days after Agha-Soltan's death.
Demonstrators began chanting "God is Great" and "Death to the dictator", slogans which protesters have been using since the election, as hundreds of police drove the protesters apart in the Behesht-e Zahra cemetery in southern Tehran, witnesses said.
Official figures have put the number killed in recent demonstrations at 20, although an MP later stated that the number was 30.
Authorities last week rejected a request by Moussavi and another opposition leader, Mehdi Karrubi, to hold an official mourning ceremony in Tehran's Mosalla Square.