Police were called in after the protesters started shouting slogans against Ahmadinejad such as 'Death to the dictator', and dispersed the crowd, the witnesses added.

Several conservative officials have asked for prosecution of Karroubi due to his rape allegations.

The hardline Ayatollah Ahmad Khatami, deputy head of the influential clergy body the Experts Assembly, was quoted by the daily Kayhan as saying that according to Islamic rulings, anybody making sexual accusations but not able to prove them should be lashed 80 times.

Karroubi himself however seems not to be intimidated by the threats and proclaimed that he will disclose all abuses in the Tehran prisons against post-vote detainees.