In a nod by authorities to allegations of abuses in the crackdown on Iran's post-election protests, the Islamic republic on Tuesday freed 140 people arrested in the turmoil and the supreme leader ordered the closure of a prison where human rights groups say jailed protesters were killed. The pro-reform opposition has been contending for weeks that jailed protesters and activists were being held in secret facilities and could be undergoing torture. Authorities appear to be paying greater attention to the complaints after the son of a prominent conservative died in prison - reportedly the same one ordered closed Monday. Opposition leader Mir Hossein Mousavi sharply condemned the wave of arrests and deaths, saying the Iranian people "will never forgive them." The last official word of the number of people in prison from the crackdown was around 500, announced several weeks ago, and arrests have continued since. The heavy crackdown was launched to put down protests that erupted following the June 12 presidential election, in which hard-line incumbent Mahmoud Ahmadinejad was declared the winner but which the opposition says was fraudulent. Among those detained are young protesters, as well as prominent pro-reform politicians, rights activists and lawyers. At least 20 people were killed, according to police, though rights groups say the number is likely far higher. A parliament committee investigating prisoners' conditions visited Tehran's main prison Evin on Tuesday, and during the visit 140 detainees connected to the protests were released, said Kazem Jalili, a spokesman for the committee, according to the semiofficial ISNA news agency. Another 150 remain in Evin because weapons were found on them when they were arrested, he said. The names of those released were not immediately known. There was no new word on the current total in prisons around the country. The head of Iran's judiciary, Ayatollah Mahmoud Hashemi Shahroudi, promised on Monday that the public prosecutor would review the situation of all the postelection detainees within a week and decide whether to release or bring them to trial, the state news agency IRNA reported. Supreme Leader Ayatollah Ali Khamenei, meanwhile, ordered the closure of Kahrizak prison, on Tehran's southern outskirts, Jalali told the Mehr news agency. "It did not possess the required standards to ensure the rights of the detainees," he said. The closure order was announced Monday in the official IRNA news agency, though the prison was not identified. Human rights groups have identified at least three protesters they say died after being detained at Kahrizak, though the reports could not be independently confirmed. Kahrizak appeared to have little role as a detention center before the election unrest, but since then many of the detainees are believed to have spent time there. Authorities' new attention to the prisoners issue comes after conservative lawmakers and politicians - the camp from which the government draws its support - expressed anger over the death of the son of Abdolhossein Rouhalamini, a prominent conservative. Rouhalamini is a close ally of Mohsen Rezai, the only conservative running against Ahmadinejad in the election. His son, Mohsen, who was arrested during a July 9 protest, was taken to a hospital after two weeks and died. The opposition news Web site Norooz reported that Mohsen had been held at Kahrizak and that his face was beaten in when his father received the body. The crackdown was carried out by police, the elite Revolutionary Guards and the pro-government Basij militia. The opposition has warned repeatedly that the detainees are being tortured to force confessions that back the government's contention that the protests were part of a foreign-backed plot to foment a "soft revolution" against the Islamic Republic. Mousavi, who claims to have won the election, said that amid the disorder of the crackdown, even the judiciary doesn't have access to all the prisoners. "All departments from intelligence to Basij say (those who arrested protesters) were not connected to them. Where are they from? Have they come from Mars?" Mousavi said. "I am sure even the judiciary is not able and has no right to visit many prisons and ask for details." In a speech Monday to a group of teachers, Mousavi denounced the arrests and deaths as a "disaster" and suggested it was worse than abuses under the regime of the pro-American shah, who was toppled in the 1979 revolution that established the Islamic Republic. "We have not experienced such a thing before the revolution. People will not forgive these acts. How is it possible that someone goes into a prison, then his body comes out," he said. He demanded a judiciary investigation in Mohsen Rouhalamini's death. "They will find out what happened. This is not what we expect from the Islamic Republic and the system," he said. The opposition has called for supporters to attend a "silent memorial" ceremony Thursday for those killed in the crackdown - raising the possibility of a new street confrontation with security forces. The opposition has asked for official permission for the ceremony. Interior Ministry official Mahmoud Abbaszadeh Meshkin said Tuesday that the ministry has not given permission for any rally. He said a ceremony does not need a ministry permit, adding that the opposition's request for a permit raises suspicions that it has "other intentions rather than a memorial."