Iran''s parliament speaker Ali Larijani on Wednesday rejected claims that some election protesters had been raped in custody and rapped the opposition leader who raised the allegations.

"The issue of detainees being sexually abused is a lie," Larijani told parliament, the official IRNA news agency reported.

"Following an investigation of detainees in Kahrizak and Evin prisons, no cases of rape and sexual abuse were found," he said, referring to the jails where most people arrested after the June election were initially detained.

Defeated presidential candidate Mehdi Karroubi claimed in a letter to powerful cleric Akbar Hashemi Rafsanjani that several male and female protesters had been raped in custody and called for an investigation.

"A number of detainees have said that some female detainees have been raped savagely. Young boys held in detention have also been savagely raped," Karroubi said in his letter dated July 29.

About 4,000 opposition supporters were arrested over the unrest that swept Iran after President Mahmoud Ahmadinejad''s disputed re-election, officials said. Most have been released, but around 200 remain behind bars. At least 110 have also been put on trial.