Police and basij militia locked down the centre of Tehran on Sunday night after crowds of anti-regime demonstrators tried to converge on central squares from across the city.
The daughter of the powerful former president, Akbar Hashemi Rafsanjani, Faezeh Hashemi, was arrested briefly, accused of "provocative behaviour", though she was later released.
Opposition and exile websites claimed there were clashes between police firing tear gas and protest groups, and reports of gunfire. iran
The government last night insisted the city was "peaceful" though the deputy police chief admitted special forces had been deployed.
The last week has seen a resurgence of the opposition Green Movement which at the time of the 2009 presidential election rallied around the defeated candidates Mir Hossein Moussavi and Mehdi Karroubi.
Two people have been killed in clashes between demonstrators and pro-government forces.
