Iranian authorities closed down pro-reform cleric Mehdi Karoubi's office yesterday, Iranian news agency ILNA reported, and a website said one of his top aides was detained.
Judiciary officials entered Mr Karoubi's office in northern Tehran and told him and others inside to leave, ILNA said. The officials then proceeded to seize documents, discs and other material of the leading reformer who came fourth in the disputed presidential election in June.
"Karoubi's office has been sealed off upon the Tehran prosecutor's order," sources quoted Esmail Gerami-Moghaddam, a spokesman for Mr Karoubi's party, as saying.
Website mowjcamp.ir said agents raided and searched the home of Morteza Alviri and took him away. It also confirmed the closure of Mr Karoubi's office.
There was no immediate comment from Iranian officials.
The report came a day after security forces raided an office run by allies of opposition leader Mirhossein Mousavi, the election runner-up, and confiscated documents, his website said.
Mr Mousavi's website said it was the premises of a committee set up by him to look into post-election events, including the number of dead and the treatment of people detained during the huge opposition demonstrations that followed the vote.
Mr Karoubi, whose newspaper was closed down three weeks ago, angered hardliners last month by saying some imprisoned protesters were raped and abused in jail. The authorities have rejected the allegation as baseless but the judiciary and Parliament have agreed to look into the issue.
Supreme Leader Ayatollah Ali Khamenei ordered the closure of Tehran's Kahrizak detention centre in July after reports of abuse there and the semi-official Mehr News Agency on Monday said a trial of people involved would start in coming days.
Mr Karoubi said on his party's website this week he had handed over films and other material about abuse of three detainees to a special investigative parliamentary committee.
Mr Ahmadinejad has suggested his opponents were behind any such incidents, saying they had "infiltrated" government forces.
The hardline President shored up his position last week when Parliament approved most of his new government ministers, after almost three months of political turmoil in the world's No. 5 crude exporter.