Iranian security agents freed two sons and four aides of Iran's most senior dissident cleric but sealed off a building that he planned to use as a seminary, one of the cleric's sons said Tuesday.

The six were detained a day earlier when police moved in to close the would-be seminary of Grand Ayatollah Hossein Ali Montazeri (search), who has pressed the hard-line clerics who run Iran to allow greater democracy.

Ahmad and Saeed Montazeri, the cleric's sons, and three of the aides were freed Monday night, Ahmad Montazeri told reporters.

The last detained aide, Reza Ziaei, was freed Tuesday. He told The Associated Press that his captors left him stranded on a dead end street after interrogating him. He said he had refused to answer their questions.

Ahmad Montazeri said Ziaei was blindfolded, handcuffed and beaten during interrogation, but said he and his brother were not mistreated while in custody. He said they were questioned about the family's plans to turn the building next to their home into a seminary where the elder Montazeri would teach.

"That mosque still remains closed, and we need facilities for the grand ayatollah to teach," Ahmad Montazeri said Tuesday. Hard-liners "don't want my father to have any facilities to teach, let alone engage in political activities."

Hossein Ali Montazeri, 81, is one of a few grand ayatollahs, the most senior theologians of the Shiite Muslim faith. He enjoys a huge following in Qom and Isfahan, his birthplace, and many reformists see him as a charismatic leader who could bring democratic changes in Iran.

He resumed teaching in September after spending five years under house arrest in Qom, a holy city 80 miles southwest of Tehran, for telling students that Iran's supreme leader, Ayatollah Ali Khamenei (search), was incompetent to issue religious rulings.

Grand Ayatollah Montazeri also accused ruling hard-line clerics of monopolizing power and ignoring Iranians' demands for democracy. Khamenei denounced him as a traitor and the mosque where he made the speech was closed.

Ahmad Montazeri said security agents on the order of the Special Clergy Court, a body dealing with clerics, used welding machines to seal off the entrance to the planned seminary.

The senior Montazeri had been the designated successor of Ayatollah Ruhollah Khomeini (search), founder of the 1979 Islamic revolution, until he fell out with Khomeini shortly before his 1989 death after complaining about powers wielded by unelected clerics.

In his first public speech in six years following the lifting of the house arrest order in September, Montazeri denounced Iran's theocratic establishment as undemocratic and urged it to allow the country's young people to choose their future.