An Iranian opposition website says security forces in Tehran staged a major clampdown following calls for protests to mark the anniversary of pro-reform leaders being placed under apparent house arrest.
Kalame.com says some "silent" protests were held Tuesday, but gave few details. The reports cannot be confirmed because of severe media restrictions on covering opposition activities.
Opposition leaders Mir Hossein Mousavi and Mahdi Karroubi have been out of the public eye for a year under what activists describe as house arrest. They led the challenge to the 2009 re-election of President Mahoud Ahmedinejad, claiming vote rigging.
Rights group Amnesty International says a block on Internet sites this week was an apparent attempt to disrupt planned protests.