By Olga Dzyubenko
BISHKEK (Reuters) - Kyrgyzstan's prime minister was on target to win a presidential election in the strategic former Soviet republic Monday, with more than half the votes counted in an election that rival candidates say was marred by fraud and poor administration.
The election is a key test of bold reforms aimed at making Kyrgyzstan the first parliamentary democracy in Central Asia after two decades of failed authoritarian rule that triggered a bloody revolution in April last year.
A trouble-free election would signal the first peaceful transfer of power in the mainly Muslim country, where both Russia and the United States operate military air bases, but several disgruntled candidates say they will reject the outcome.
With 53 percent of ballots counted, Moscow-backed Prime Minister Almazbek Atambayev had 65 percent of the vote, an outright majority that would avoid the need for a second round run-off against a potentially strong rival from the south.
The results could yet change as votes are tallied around the landlocked, mountainous country of 5.5 million people. The Central Election Commission said voter turnout was slightly over 60 percent.
Atambayev's two main challengers from a field of 16 candidates were each polling below 15 percent. Both enjoy strong nationalist support in the poorer south of the country and have vowed to contest any result they believe to be unfair.
Though both have insisted their subsequent actions will be lawful, they have refused to rule out street protests. Any show of public discontent raises the threat of renewed violence and could accentuate a north-south political and cultural divide.
Atambayev, born in the Russian-leaning north of Kyrgyzstan, is the flag-bearer of reforms set in motion by outgoing leader Roza Otunbayeva when she assumed the presidency in a caretaker role after the revolution.
The reforms have watered down the powers of the president and established parliament as the main decision-making body.
Both of Atambayev's main challengers, Adakhan Madumarov and Kamchibek Tashiyev, say they wish to reverse these reforms.
Madumarov, in third place with 53 percent of votes counted, was among a group of candidates who declared the results invalid even before polls closed Sunday, saying that many voters had been left off the electoral roll.
The other leading southern candidate, former emergencies minister Kamchibek Tashiyev, has said "millions" would take to the streets if they believed the elections to be unfair. He was placing second, with 14 percent of the vote.
The next president will be allowed by the current constitution to serve a single 6-year term and will appoint the defense minister and national security head.
Stamping out graft will be a major challenge to the next leader of a country that ranked level with the Democratic Republic of Congo in Transparency International's 2010 Corruption Perceptions Index.
Per capita GDP in Kyrgyzstan, at below $1,000, is less than a tenth of that in its oil-rich neighbor Kazakhstan. The economy relies heavily on remittances from migrant workers and the production of a single gold mine.
(Additional reporting and writing by Robin Paxton; editing by Tim Pearce)