The opposition in Ukraine is urging supporters to march to the office of outgoing President Leonid Kuchma to protest Sunday's election.
Some 200,000 demonstrators are already rallying in Kiev in the cold and snow as part of continuing protests over the presidential poll.
Opposition leader Viktor Yushchenko has declared himself the winner. But election officials say with nearly all the votes counted, he trails Prime Minister Viktor Yanukovych by three percentage points.
Mr. Yushchenko symbolically took the oath of office at an emergency session of parliament focusing on the election.
The opposition alleges widespread fraud in favor of the prime minister.
U.S. and European observers reported indications of extensive voter fraud. Russian President Vladimir Putin called European criticism inadmissible because final results have not been announced.
Some Ukrainian diplomats in Washington have called on Kiev to respect the true will of the people.