KIEV — Ukraine's opposition leader Viktor Yanukovych claimed a slender victory in a presidential election on Monday that could tilt the former Soviet republic back toward Moscow, but bitter rival Yulia Tymoshenko refused to concede.

With a little more than 90 percent of votes counted early on Monday, election officials gave Yanukovych 48.49 percent and Prime Minister Tymoshenko 45.86 percent, a margin of 2.63 percentage points.

Tymoshenko's camp, alleging fraud, offered a "parallel count" late on Sunday that saw her edging out her rival. The margin in the official results made it likely that Tymoshenko would mount a legal challenge, prolonging the uncertainty.

The official results signaled a comeback for the rough-hewn Yanukovych, tagged as Moscow's stooge five years ago when street protests overturned results that initially gave him victory in an election tainted by fraud.

A Yanukovych victory could see the country of 46 million people shift back towards former Soviet master Russia after five years of infighting and a sliding economy turned the euphoria of the Orange Revolution into frustration and disappointment.

Both candidates pledged integration with Europe while improving ties with Moscow, but Tymoshenko is seen as more pro-Western. Yanukovych is unlikely to pursue membership of NATO, an “Orange” goal that infuriated neighboring Russia.

Yanukovych, 59, a beefy ex-mechanic who wants better ties with Moscow, called on Tymoshenko, 49, to resign as prime minister. But Tymoshenko's team said they had counted 85 percent of votes and she was leading by 0.8 percent.

Each side accused the other of fraud, but Tymoshenko stopped short of repeating a threat she made last week to call people out onto the streets if she believed that the election was unfair.

"I think that Yulia Tymoshenko should prepare to resign. She understands that well," Yanukovych said in a television interview. Exit polls put him 3 to 4 points ahead.

If the latest figures continue as expected, Yanukovych would be the first president since independence in 1991 not to receive more than 50 percent of the vote, although elections in the 1990s were not always judged free and fair.

Some analysts said given the relative weakness of his position he might seek some compromise with Tymoshenko, and they did not rule out the possibility that the two camps were talking to each other on this.

Under this scenario, Tymoshenko might concede defeat in exchange for remaining prime minister and living to fight for the presidency another day.

Tymoshenko was the co-architect of the 2004 revolution with pro-Western President Viktor Yushchenko, but their relationship quickly soured.

Looking stern in front of reporters, the fiery prime minister urged her team to "fight for every result, every document, every vote." The tone was moderate, and analysts said they doubted that Tymoshenko could stage a repeat of 2004.

A disputed outcome would further delay Ukraine's chances of repaying more than $100 billion of foreign debt and nursing its sickly economy back to health after a 15 percent collapse last year.

In Russia, the source of the gas that flows through Ukraine's pipeline network to the West, the election was closely watched but state-controlled media avoided taking sides.

Sunday's vote, conducted in freezing temperatures and snow, appeared to reflect widespread disillusion among Ukrainians that the Orange Revolution failed to deliver prosperity or stability.

Yushchenko placed a humiliating fifth in the first round of the election in January.

The $120 billion economy has been battered by a decline in the value of Ukraine's steel and chemicals exports that has hammered the hryvna currency, slashed budget revenues and undermined the domestic banking system.

Voters were unenthusiastic about either candidate but seemed to feel that Yanukovych, a former prime minister who stressed the fight against poverty, had the best chance of restoring order.

"We lost five years of our lives thanks to Yushchenko and Tymoshenko," said Oleg Nochvyn, a miner in his fifites in the eastern region of Donetsk.

"For five years they were promising us, ‘Tomorrow will be better.’ Well, I get up the next day and it's worse than the day before ... Under Viktor Fyodorovich [Yanukovych] we had everything — economic growth, everything was getting better."

Regardless of the outcome, squabbling was set to continue, reflecting the country's broader divisions. Ukraine is divided almost equally between a Russian-leaning east and south and a Western-friendly center and west.

With a Yanukovych victory, Tymoshenko can expect to be ousted as prime minister by a vote of no confidence in the parliament. Yanukovych will then try to form a new coalition to get his own ally into the role or call a snap parliamentary election.