Hajeih Khanom Rabani died Saturday, around four months after her husband died at the age of 87.
Once a student of Ayatollah Ruhollah Khomeini, the founder of the Islamic republic, Montazeri became the spiritual leader of the so-called Green Movement that emerged after disputed June presidential elections.
Saeed Montazeri, their son, said security forces and plainclothes police tightened security measures during the weekend in Qom amid funeral preparations, reports Radio Zamaneh, a Persian news service in the Netherlands..
"Tens of government vehicles brought the body without allowing any access to it even by her family," he said. "They made a small stop at the shrine and quickly removed her form the premises."
Supporters of the opposition movement in Iran said riot police were dispatched to the cemetery in Qom hours before weekend mourning ceremonies.
Iranian police and anti-government protesters clashed during the December memorial service for Montazeri in Isfahan.