Bishkek: Kyrgyzstan's moderate prime minister emerged on Monday as the next president of the violence-scarred nation after a decisive election victory, but his vanquished rivals claimed the ballot was rigged.

Almazbek Atambayev, a close ally of outgoing President Roza Otunbayeva who took power after a 2010 uprising ousted the regime of Kurmanbek Bakiyev, won 63 percent of the vote in Sunday’s polls, the central election commission said.

The crushing victory over his two nationalist rivals -- who garnered less than 15 percent apiece -- gave Atambayev the presidency without the need for a potentially tricky second round.

Atambayev, 55, now faces the task of healing the wounds of a divided nation that within the space of a year in 2010 endured the bloody revolution that ousted Bakiyev and horrific inter-communal violence that killed some 470.

"According to the initial results, Almazbek Atambayev has been elected the president of Kyrgyzstan," central election commission chief Tuigunaly Abdraimov told reporters.

"There will be no second round. Atambayev won more than half of the votes and we can say that he won in the first round."

The future of the nation of 5.3 million is closely watched by the West, which uses Kyrgyzstan as a hub for transit operations for the campaign in Afghanistan. It is the only country in the world to house US and Russian bases.

Kyrgyzstan is also the only nation in ex-Soviet Central Asia, a region dominated by strongmen leaders who have clung on to power for years, to hold keenly contested presidential elections.

But Atambayev's two leading rivals out of 15 challengers -- the one-time parliament speaker Adakhan Madumarov and former boxer Kachimbek Tashiyev – immediately denounced the elections as a fraud and warned of protests.

The campaign team of Tashiyev accused the authorities of "brazenly making up numbers that are far removed from reality."

"We do not intend to recognise these elections," Tashiyev's campaign office said.

The charismatic ex-speaker Madumarov also accused the authorities of overseeing "unprecedented violations".

"If the election results are falsified, we will definitely launch protest action," Madumarov said. "I will defend the vote of each one of my supporters."

In the two decades since the fall of the Soviet Union, Kyrgyzstan has not once had a peaceful transition of presidential power.

The April 2010 uprising was the second for independent Kyrgyzstan after the 2005 Tulip Revolution that ousted post-Soviet leader Askar Akayev and installed Bakiyev in his place.

In these tense circumstances, the conclusions of an international observer mission, due to be announced at around 13:30 IST, will be closely watched to see if they give the poll a relatively clean bill of health.

The central election commission chief Abdraimov reported several isolated incidents of voting irregularities, including attempts to stuff ballot boxes in certain regions, but stressed these were small in scale.

"Results at certain precincts will probably be annulled," Abdraimov said. "But these violations cannot affect the results themselves."

In initial comments yesterday, the OSCE's Office for Democratic Institutions and Human Rights praised the choices available to voters, but criticised imperfect registration lists that had kept some people from voting.

Even the outgoing president's own son Atay Sadybakasov said he had been told he was not registered to vote at his polling station.

According to the results based on 97 per cent of the electoral precincts, Atambayev won 63.0 per cent, Madumarov 14.8 per cent and Tashiyev 14.3 per cent.

The south of Kyrgyzstan remains tense after the 2010 ethnic violence between the Kyrgyz majority and the Uzbek minority communities that raised questions at the time about its future viability as a nation.

On the eve of the vote, Human Rights Watch said a priority for the new president was ensuring fair trials over the 2010 unrest. It said the authorities were targeting Uzbeks even though they had borne the brunt of the violence.