Ukraine's parliament has declared last Sunday's presidential run-off election in the former Soviet republic invalid.

Lawmakers approved a resolution declaring that the run-off was subject to many irregularities and failed to reflect the intention of voters. They also expressed no confidence in the country's central election commission, which had declared pro-Russian Prime Minister Victor Yanukovych the victor

Tens of thousands of demonstrators backing western-leaning challenger Viktor Yushchenko have massively protested in Kiev and other cities against the decision.

The parliamentary decisions are not legally binding but give added weight to Monday's Supreme Court consideration of reports by the opposition and international monitors of widespread election fraud.

Mr. Yushchenko late Friday called for fresh elections on December 12.

Meanwhile, a multilateral committee tasked with resolving the political stalemate and made up of representatives of both sides is scheduled to meet today.

President Bush says he hopes the Ukrainian election dispute is resolved in a way that, in his words, "brings credit to the Ukrainian government."

Mr. Bush said Friday allegations of vote fraud in Ukraine must be investigated, and the international community is watching the situation very carefully.

Earlier, a U.S. State Department official said Washington is supporting efforts by Poland and the rest of the European Union to mediate the dispute.

Russian Foreign Minister Sergei Lavrov sharply criticized what he called attempts by Western countries to influence the outcome of the election. He said Ukrainians alone should decide their country's future.

Western nations have rejected official results declaring Kremlin-backed Prime Minister Viktor Yanukovych the winner of Sunday's election. They say the election fell far short of international democratic standards.