DUBAI, United Arab Emirates  Some prisoners say they watched fellow detainees being beaten to death by guards in overcrowded, stinking holding pens. Others say they had their fingernails ripped off or were forced to lick filthy toilet bowls.

The accounts of prison abuse in Iran’s postelection crackdown  relayed by relatives and on opposition Web sites  have set off growing outrage among Iranians, including some prominent conservatives. More bruised corpses have been returned to families in recent days, and some hospital officials have told human rights workers that they have seen evidence that well over 100 protesters have died since the vote.

On Tuesday, the government released 140 prisoners in one of several conciliatory gestures aimed at deflecting further criticism. President Mahmoud Ahmadinejad issued a letter urging the head of the judiciary to show “Islamic mercy” to the detainees, and on Monday Iran’s supreme leader, Ayatollah Ali Khamenei, personally intervened and closed an especially notorious detention center.

But there are signs that widespread public anger persists, and that it is not confined to those who took to the streets crying fraud after Mr. Ahmadinejad’s landslide victory last month. Several conservatives have said the abuse suggests a troubling lack of accountability, and they have hinted at a link with Mr. Ahmadinejad’s recent willingness to defy even the venerated Ayatollah Khamenei.