A reformist candidate defeated in the Iranian presidential election has claimed that arrested protesters have been "savagely raped" while in custody.
Mehdi Karroubi, who has led protests to overturn the result of the June 12 vote, said that both women and young boys had been victims of assault.
His allegations, made in a letter to the former president, Hashemi Rafsanjani, follow a number of individual claims made by Iranian blogs and foreign media.
They were revealed as the head of the police admitted there had been mistreatment of prisoners detained in the aftermath of the election.
Politicians from across the political spectrum in Iran have alleged that a number of protesters have died while in police custody.
Mr Karroubi posted a copy of his letter on his website on Sunday. "A number of detainees have said that some female detainees have been raped savagely," he wrote.
"Young boys held in detention have also been savagely raped. The young boys are suffering from depression and serious physical and mental damage."
Mr Karroubi wrote the letter to Mr Rafsanjani in his role as head of the Assembly of Experts, which is responsible for supervising the performance of the supreme leader, Ayatollah Ali Khamenei. But Mr Rafsanjani has also emerged as a key figure in the split in the Iranian regime's leadership, challenging the government's handling of the election and the post-election protests.
Mr Karroubi said in the letter that his informants were in "sensitive positions". But a number of Iranian blogs have taken up the case of Taraneh Moussavi, 28, who was picked up a week after the election by plain-clothed police while awaiting a speech by Mir Hossein Mousavi, the principal reformist challenger.
She disappeared, after being separated from others detained at the same time, but some weeks later her family were telephoned to be told that she had been hospitalised after rupturing her womb and anus in "an unfortunate incident".
By the time they arrived at the hospital she had disappeared again, and her body was later found, burned, in the desert to the west of Tehran.
She is thought previously to have been taken to Evin Prison in Tehran, the main base for holding political detainees.
The police chief, General Ismail Ahmadi Moghaddam, said that there had been mistreatment of protesters taken to Kahrizak prison, in southern Tehran, which is normally used to hold dangerous criminals. But he said the only deaths were from a viral illness spread by overcrowding.
Opposition leaders and even some government supporters claim that at least three protesters were tortured and killed in the jail, including the son of a senior aide to another defeated candidate, the conservative Mohsen Rezaei, who has led calls for an inquiry.
The prosecutor-general, Ghorban Ali Dorri Najafabadi, said: "Unfortunately, negligence and carelessness by some officials caused the Kahrizak incident, which is not defendable.
"During early days, it is possible there were mistakes and mistreatment due to overcrowding in the prison."
The prison was closed in July, and three warders arrested.
