Losing presidential candidate Viktor Yanukovych (search) appealed the results of last month's election to Ukraine's Supreme Court, arguing that the election be declared invalid because of massive fraud, a court spokeswoman said Wednesday.

Preliminary results from the Dec. 26 election show opposition candidate Viktor Yushchenko (search) winning a sound victory.

Yanukovych's campaign manager Taras Chornovil said Tuesday's filing was just an "intermediate" appeal, and the main challenge will be submitted only after the Central Election Commission announces final results.

Yanukovych will ask the court to declare that it is "impossible to establish the result of the election" due to massive fraud, Chornovil said.

The appeal would be identical to the one Yushchenko used in challenging the Nov. 21 presidential runoff, in which Yanukovych claimed victory, he said.

That runoff triggered the so-called Orange Revolution (search) on Kiev's streets, with protests that lasted 17 days and culminated in the Supreme Court agreeing with Yushchenko that fraud made it impossible to determine a winner in the Nov. 21 vote.

The court then stripped Yanukovych of his victory and ordered the Dec. 26 revote.

Yanukovych insists he remains the legitimately elected president and has vowed to fight the results of the Dec. 26 revote. However, last week, the Central Election Commission rejected his appeal, saying he failed to prove massive fraud.

International observers said they saw no evidence of the mass vote-rigging that marred the Nov. 21 voting.

The commission was ready to announce the final results but election law prohibits them from declaring a president-elect while appeals are pending with the commission, press secretary Zoya Sharikova said. Yanukovych's campaign files new appeals every day, she said.

Yanukovych, whose resignation from his post as prime minister was formally accepted Wednesday, has said he holds little hope that the Supreme Court will rule in his favor, but he vowed to carry on the fight.

"The Supreme Court a long time ago turned into an organ that just takes politically oriented decisions," Chornovil said.

Court spokeswoman Lianna Shlyaposhnikova said a three-judge panel will consider Yanukovych's appeal Thursday. The court already has rejected other minor appeals, but this is the first to address the election in its entirety, asking that the vote in the country's 225 districts be invalidated.

Yushchenko, who is vacationing in the western Carpathian mountains with Georgian President Mikhail Saakashvili (search), has expressed confidence that his victory will stand. Saakashvili, who also rose to power after mass protests, has become one of Yushchenko's strongest foreign allies.