A reformist widely regarded as pro-Western by pundits at home and abroad,
Yushchenko defeated Prime Minister Viktor Yanukovych 51.99 percent to 44.19 percent, Reuters and Interfax news agency reported.
Ballots were reportedly cast against both candidates by 2.34 percent of voters.
Yanukovych ChallengeYanukovych
vowed last night to mount a legal challenge to the results of the election as returns showed his reformist opponent with an insurmountable lead.
"I will never recognize this defeat because there were violations of the constitution and of human rights in our country," Yanukovych said last night.
Yanukovych stressed that he has not urged his supporters to mount public demonstrations, AP reported.
The Yanukovych campaign team has collected almost 5,000 complaints so far concerning the fairness of the balloting, the prime minister told reporters.
Yanukovych criticized election-law reforms passed between the abortive runoff and the 26 December vote that restricted home voting, which was blamed for some of the fraud that marred the November vote. That restriction was
nullified by the Constitutional Court on the eve of the ballot.
Candidates have seven days to appeal from the release of the final preliminary tally.
International ReactionPolish President Aleksander Kwasniewski has already congratulated the opposition leader on his victory, according to a press release from Kwasniewski's office quoted by Reuters yesterday.
The Organization for Security and Cooperation in Europe (OSCE) said yesterday that the vote shows the country has taken "a great step forward toward free and fair elections."
The head of the OSCE observer mission, Bruce George, said this was the general view among the monitoring organizations.
"I am much happier to be in a position to announce that it is the collective judgment of these organizations represented here that the Ukrainian elections have moved substantially closer to meeting OSCE and other European and international standards," George said.
However, George added that the election was not perfect and that the mission's final report will detail what observers saw as its shortcomings.
The repeat vote was monitored by some 12,000 international observers.
European Union High Representative for Common Foreign and Security Policy Javier Solana called on Ukraine's political leaders to work together to unite the country after the divisive election.
U.S. Secretary of State Colin Powell broke the official silence in Washington today over the vote and called the Ukrainian election "a historic moment for democracy." He said it appeared the Ukrainian people had had the opportunity to choose their own government and added the election appeared to have been "full and free."
Lingering DiscordBut the results from the 26 December vote suggest once more that Ukraine is deeply divided, with the western and central regions backing Yushchenko while the east mostly supported Yanukovych.
Yanukovych's senior political allies in some of the eastern regions threatened in November to seek autonomy, something they have since moved away from. A member of parliament from the Social Democrat Party-united, which supported Yanukovych, Ihor Shurma, suggested some kind of devolution might happen -- but not for a while.
"Perhaps a federal model will be beneficial for Ukraine, but not today. Ukraine is not ready for that today," Shurma said. "Economically it's not strong enough. At present it faces many risks. Therefore, it is not appropriate to raise this question at this time."
Recent Stories:"Yanukovych Pledges To Challenge Ukraine's Vote Results""Analysis: Will Ukraine Now Orient Itself Toward The West?""Ukraine's Presidential Election Appears To Go Smoothly""Ukrainian Court Throws Out Electoral Changes"[For more RFE/RL coverage and analysis, see our dedicated "Ukraine's Disputed Election" website.]