Hossein Karroubi told The Guardian his father was confined after he issued a call for a demonstration Monday to support Egyptian anti-government protesters. He said security officers kept him away when he tried visiting his father Thursday at his home in Tehran, and only his mother is allowed to see her husband.
"It is the first time that the government has restricted my father this far so that even us, as close family members are also banned from visiting him, this is obviously a move aimed at intimidating the leaders of the opposition for Monday's protest," Hossein Karroubi said.
Thousands of Iranians appear to be planning to join demonstrations Monday like those after the 2009 presidential election.
Karroubi, a leader in the 1979 Islamic revolution, ran for president in 2005 and 2009 as a critic of the government. He calls himself a moderate and says the current leaders have strayed from the principles of Ayatollah Ruhollah Khomeini.
Web sites report the arrest of other Iranian opposition leaders, the Guardian said.