Iran's Supreme Leader appointed Ayatollah Sadeq Larijani as the new head of the country's judiciary on Saturday, state television reported.
Some reformist websites had recently reported that Larijani was hesitant to accept the position because of the mass arrests of moderate detainees over unrest that erupted after the country's disputed June 12 presidential election.
He will face controversy straight away -- the semi-official ISNA news agency said a new trial would start on Sunday of 25 opposition supporters detained after the election.
Larijani, a brother of parliament speaker Ali Larijani and a member of Iran's hardline constitutional watchdog the Guardian Council, replaces Ayatollah Mahmoud Hashemi-Shahroudi whose 10-year term has ended.
Supreme Leader Ayatollah Ali Khamenei said in a letter to Larijani that he hoped the judiciary would flourish under him. Larijani, a cleric born in Iraq's holy Shi'ite city of Najaf, will serve a five-year term.
Iran arrested hundreds of people after the vote during the country's worst street unrest since its 1979 Islamic revolution.
After police and security forces quelled the street turmoil, the leadership put on trial more than 100 moderates, despite the damage it might inflict on the government's legitimacy and relations with the West.
"Some 25 more detainees will go on trial on Sunday," ISNA said, without naming them. They will be the third group to appear in court.
The losing candidates say 69 people were killed in unrest that erupted after the vote. The figure is more than double the official toll of 26.