Defeated candidate Mirhossein Mousavi demanded on Sunday that Iran's presidential vote be annulled and urged more protests, while tens of thousands of people hailed the victory of President Mahmoud Ahmadinejad, Reuters reported.
Mousavi's supporters again took to the streets after violence on Saturday, clashing with police in protests that have underscored harsh political divisions exposed by Friday's disputed election.
In a statement on his website, Mousavi said he had formally asked the Guardian Council, a legislative body, to cancel the election result. "I urge you, Iranian nation, to continue your nationwide protests in a peaceful and legal way," he added.
The unrest that has rocked Tehran and other cities since results were declared on Saturday is the sharpest expression of discontent against the Islamic Republic's leadership for years.
The election result has disconcerted Western powers trying to induce the world's fifth biggest oil exporter to curb its nuclear program. U.S. President Barack Obama had urged Iran's leadership "to unclench its fist" for a new start in ties.
Ahmadinejad waved and smiled at the flag-waving partisans thronging the capital's Vali-e Asr square to applaud the victory he won by a surprising 63 percent of the vote.