Ukraine's prime minister, Viktor Yanukovych, lost important legal challenges Thursday, narrowing the likelihood that he will be able to overturn the results of Sunday's presidential election.  Those results, yet to be certified, give pro-western opposition leader Viktor Yushchenko, the win.

Thursday's rulings against Mr. Yanukovych by both Ukraine's Supreme Court and the Central Election Commission mean he has little recourse now to try and overturn his opponent's apparent win.  It also means that Mr. Yushchenko's efforts to press ahead with assuming power could be accelerated.

For the past two days, Ukraine's Supreme Court has been examining four complaints filed by Mr. Yanukovych about what he says were widespread violations on voting day.  The court overruled the first claim on Wednesday, and followed up by rejecting the remaining three late Thursday. 

According to court officials, the first claim was thrown out because it was filed too late.  The officials say the others were not justified.  The ruling is final and cannot be appealed.

Ukraine's Central Election Commission followed suit several hours later, rejecting Mr. Yanukovych's claim disputing the final preliminary election results, which give Mr. Yushchenko an 11-percentage-point lead over Mr. Yanukovych.

Sunday's election was a re-run of the runoff between Mr. Yanukovych and Mr. Yushchenko, which was held after the Supreme Court overturned the results of the initial runoff, citing voter fraud. The prime minister had been declared the winner of that earlier vote.

The deputy commission chief of Ukraine's Central Election Commission, Marina Stavniitchuk, says Mr. Yanukovych's claim was denied for "a lack of convincing evidence."

Ms. Stavniitchuk says Mr. Yanukovych neither proved massive violations during Sunday's vote, nor claimed enough discrepancies to influence the vote's overall outcome.

Mr. Yanukovych submitted 27 volumes of complaints to the commission earlier this week.  The complaints mainly focused on his view that millions of the sick and elderly were denied their right to vote because of recent new changes to Ukraine's electoral law.

Assessing the overall conduct of the vote earlier this week, international election monitors said it was unfortunate the changes were made so late in the election cycle.  But the observers say they did not adversely affect the election so as to skew the results.

The observers, who numbered in the tens-of-thousands, also said the December 26 ballot was a great improvement over the last round in November.

Mr. Yanukovych did not react directly to Thursday's decision, which leaves him only one avenue of appeal through the Supreme Court. But Yanukovych Spokesman Nestor Shuffrich says the prime minister's camp does not feel the commission even attempted to investigate the claim.

Mr. Shuffrich says the prime minister will exercise his right to appeal in the Supreme Court, but he says "our side holds out little hope the justices will be impartial."