Iranian opposition leader Mehdi Karrubi's website, Sahamnews, says Iranian paramilitaries have surrounded Karrubi's house.
The report says "more than 50 members of the Basij [a volunteer force loyal to Supreme Leader Ayatollah Ali Khamenei] and plainclothes men that covered their faces surround his house."
Plainclothes officers equipped with tear gas, handcuffs, and batons had reportedly arrived at the house late on August 30.
Karrubi previously said he intended to attend an annual day of anti-Israel rallies in Iran known as Quds (Jerusalem) Day, which takes place on September 3.
Karrubi and fellow opposition leader Mir Hossein Musavi, both candidates in the country's disputed 2009 presidential election, have previously been attacked by supporters of the government.
compiled from Reuters reports