He has also called on authorities to release hundreds of people detained in the turbulent aftermath of the election, including leading reformists, journalists and rights lawyers.

Rafsanjani will lead the prayers after two months of absence. Some of his relatives, including his daughter Faezeh, were arrested briefly for taking part in pro-Mousavi rallies.

State media say at least 20 people were killed as protesters clashed with riot police and members of the Basij militia, but some rights activists believe the figure is higher.

The authorities and Mousavi blame each other for the bloodshed. Hardliners have called for Mousavi to be put on trial.

Iran has accused Britain and the United States, which have criticised a crackdown on opposition protests, of interfering in its internal affairs. London and Washington reject the charge.