Opposition websites said Sunday hundreds of police wielding batons tried to disperse hundreds of demonstrators who took to the streets of the capital. The websites say police also ordered shops to close early to prevent crowds from gathering.
The opposition had called for a silent rally to remember the 2009 vote that reformists say was rigged to ensure Mr. Ahmadinejad's victory.
Authorities responded to the protests with a harsh crackdown that killed scores of people. The dispute over the election results became Iran's worst unrest since the 1979 Islamic revolution.
Iranian Supreme Leader Ayatollah Ali Khamenei praised the recent revolts in Egypt and Tunisia as an Islamic awakening, akin to the 1979 revolution that ousted Iran's Shah. However, the Iranian government has crushed anti-government protests in its own country and has avoided support of the popular uprising against long-time ally Syrian President Bashar al-Assad.