TEHRAN, Iran (CNN) -- Amid turmoil over the treatment of post-election detainees and controversy over the mass trials of political figures, Iran's supreme leader on Saturday appointed a new judiciary chief, Iranian media reported.
Ayatollah Ali Khamenei speaks during the announcement that Sadeq Larijani, right, will head Iran's judiciary.
Ayatollah Ali Khamenei tapped Sadeq Larijani -- brother of Iran's powerful parliamentary speaker, Ali Larijani -- to replace Hashemi Shahroudi, a vocal hardliner against the opposition movement, who finished his 10-year term, the semi-official Mehr news agency reported. Another brother, Mohammad Javad Larijani, is the secretary-general of the judiciary's human rights office.
The development is significant in that the two brothers now head two of the three branches of Iran's government, and tensions between Ali Larijani and hardline President Mahmoud Ahmadinejad have emerged as the president tried to assemble his Cabinet for his second term.
Sadeq Larijani makes the transition as a third round of detainees arrested in the aftermath of the Islamic republic's disputed presidential election were scheduled to appear in court Sunday, the semi-official Fars news agency said.
The mass trial of about 100 Iranians is being held in the Revolutionary Court. Reformist politicians, lawyers and journalists are among those accused of protesting in an attempt to overturn government leadership. More than two dozen detainees were scheduled to be on trial Sunday, according to media reports, although it is not clear whether it will be the defendants' first appearance in court.
Among the defendants who have been on trial this month are Seyyed Mohammad Abtahi, a former Iranian vice president; Maziar Bahari, an Iranian-Canadian reporter for Newsweek magazine; and Kian Tajbakhsh, an Iranian-American scholar.
Street protests and a brutal government crackdown followed the June 12 presidential election, leading to the arrests of more than 1,000 people. The official death toll from the post-election unrest is 30, although opposition leaders reportedly have said it's more than twice that figure.
The new judiciary chief's brother, Ali Larijani, spent the last week dismissing allegations by Iran's opposition that post-election detainees were raped while in custody, according to state-run media.
Larijani said that a special panel of Iran's parliament, or Majlis, conducted a "precise and comprehensive inquiry" into the treatment at Tehran's Evin and Kahrizak prisons, and found "no cases of rape or sexual abuse," government-funded Press TV reported.
A spokesman for Iran's Foreign Ministry also denied that prisoners had been tortured.
"What kind of talk is this? There was never any pressure used against these people," Hassan Qashqavi said Monday, according to the semi-official Mehr news agency.
They were responding to accusations made by opposition candidate Mehdi Karrubi who, along with opposition leader Mir Hossein Moussavi, ran against hardline President Mahmoud Ahmadinejad in the June 12 election. Iran's election authority declared Ahmadinejad the overwhelming winner of the race, sparking hundreds of thousands of Iranians to take to the streets in protest.
Iranian opposition figures, including Karrubi, have compared the treatment of the detainees to the abuse of political prisoners under the "oppressing regime" of the shah, who was overthrown by the Islamic Revolution in 1979.
In an open letter to former president Ali Akbar Hashemi Rafsanjani posted Saturday on his party's Web site, Karrubi says an "impartial committee" is needed to "investigate these tragedies with transparency until they are resolved."
"Some of the former detainees have told of such brutal and violent, repeated rapes of the young women [in detention] that have caused irreparable damage to their reproductive systems," Karrubi says in the letter. "Others have raped our detained young men with such brutality that they [the victims] have been afflicted by depression and are no longer speaking with anyone and refuse to leave the dark corners of their houses."
Larijani on Wednesday challenged Karrubi to "present evidence of such outrages" for the Majlis to investigate, according to Press TV.