Iranian riot police have clashed with hundreds of pro-reform protestors in central Tehran in the latest unrest over last month's disputed election.
A witness said demonstrators were chanting slogans against President Mahmoud Ahmadinejad and the government.
The witness said police beat protestors who had gathered in Tehran's Haft-e Tir square in defiance of a ban on such demonstrations following the 12 June election, which the opposition says was rigged in favour of Ahmadinejad.
Riot police reportedly put dozens of protestors into their cars and took them away.
The clash erupted four days after similar confrontations between police and protestors for the first time in weeks on Friday after former President Akbar Hashemi Rafsanjani declared the Islamic Republic in crisis and said there were doubts about the election result.
The authorities reject opposition charges of vote rigging.
The election stirred the most striking display of internal unrest in Iran, the world's fifth biggest oil exporter, since the 1979 revolution and exposed deep rifts in its ruling elite.
At least 20 people died in post-election violence last month.
Mr Mousavi and the authorities blame each other for the bloodshed. Riot police and religious Basij militia eventually suppressed June's protests, but Mr Mousavi has remained defiant.
Mr Mousavi, who came second in the election, and fourth-placed pro-reform cleric Mehdi Karoubi have continued to dispute the official election result, even though Supreme Leader Ayatollah Ali Khamenei has endorsed President Ahmadinejad's election victory.
Earlier today, Iran's police chief Esmail Ahmadi-Moghaddam accused the opposition of 'inciting sedition' after the election and said his force would act firmly to uphold the law, the official IRNA news agency reported.
His deputy Ahmad-Reza Radan separately said there were rumours of new 'illegal gatherings' in Tehran today but that the security forces would firmly confront any such protests, the semi-official Fars News Agency reported.
