ranian riot police are reported to have arrested a number of pro-reform protesters in Tehran after demonstrations turned violent.
Police clashed with hundreds of people marching despite a ban on public gatherings since the disputed election in June, Reuters news agency said.
The re-election of President Mahmoud Ahmadinejad sparked widespread protests and allegations of vote-rigging.
Defeated candidate Mir Hossein Mousavi has continued to contest the result.
Mr Mousavi has issued statements opposing the election result, saying detention of protesters would not end opposition.
Witnesses said hundreds or even thousands of people took to the streets of Tehran on Tuesday afternoon, although curbs on the international media mean it is difficult to verify reports from Iran independently.
From BBC news