Iran's Supreme Leader appointed hardline cleric Ebrahim Raisi as the new head of the judiciary on Thursday, the state news agency IRNA said.
The appointment of Raisi, 58, a protégé of Supreme Leader Ayatollah Ali Khamenei, positions him to undermine the influence of moderates under President Hassan Rouhani in Iran's complicated multi-tiered power structure.
"I am appointing you as the head of the judiciary..., as a person who is familiar with the judiciary after years of serving inside the system," Khamenei said in a statement carried by IRNA.
Despite Raisi's role in overseeing the execution of political prisoners in the late 1980s, his promotion will make him a contender to succeed Khamenei.
Raisi is a mid-ranking figure in Iran's Shi'ite Muslim clergy but has been a senior official for decades in the judiciary, which has enforced clerical dominance over the country since the 1979 Islamic Revolution.
Khamenei appointed Raisi in 2016 as custodian of Astan Qods Razavi, an organization in charge of a multi-billion-dollar religious foundation that manages donations to Iran's holiest shrine in the northern city of Mashhad.
Raisi, who lost to Rouhani in the 2017 presidential election, had barely reached adulthood by the 1979 revolution but rose quickly through the ranks.
In 1988, he was one of four sharia (Islamic law) judges behind the mass execution of leftists and other dissidents.