Kyrgyzstan voted Sunday to elect a new president who will determine whether bold reforms to create Central Asia's first parliamentary democracy will succeed in the divided and restive former Soviet republic.

A clean election would signal the first peaceful handover of the presidency in the mainly Muslim country after 20 years of failed authoritarian rule, the culmination of reforms set in motion after a bloody revolt toppled the president last year.

But less than an hour before polls closed, six of the 16 candidates said they would reject the outcome. Some said they had witnessed multiple voting, while others said poorly prepared voter lists had excluded many people from the ballot.

Tens of thousands of voters couldn't vote in line with their constitutional rights. They are outraged, said Adakhan Madumarov, one of two serious challengers to the Moscow-backed Prime Minister Almazbek Atambayev.

Instability in Kyrgyzstan worries the United States and Russia, which operate military air bases in the country of 5.5 million people and share concerns over drug trafficking and the possible spillover of Islamist militancy from Afghanistan.

We want an honest president who can uphold the law, somebody who will not allow the country to be divided by clans or by north and south, said 43-year-old schoolteacher Aida, who declined to give her second name.

Those who took power after an April 2010 revolution, led by outgoing President Roza Otunbayeva, have watered down the powers of the president and established parliament as the main decision-making body in Kyrgyzstan.

Atambayev, the pro-business prime minister, is the flag-bearer of these reforms. His policies are closest to those of Otunbayeva, who will step down at the end of 2011.

A parliamentary system is more suited to the nomadic spirit of the people, Atambayev told reporters after casting his vote. After 20 years, we are convinced that we don't need absolute power, which can transform itself into dictatorship.

Opinion polls have made Atambayev, 55, the clear favourite.

He's a grafter, said retired construction worker Nikolai Dubovik, 77, who braved the first snow of winter to vote early at a school in the capital Bishkek.

But analysts question whether he can secure the outright majority required at the first attempt. If he falls short, he will face a strong challenger from the south in a run-off.

Per capita GDP in Kyrgyzstan, at below $1,000, is less than a tenth of that in its oil-rich neighbour Kazakhstan. The economy relies heavily on remittances from migrant workers and the production of a single gold mine.

Stamping out graft will also 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.

The current authorities have done a lot, but not everything they promised, said 53-year-old architect Kubanbaike Aliaskarov. The price of gasoline is hitting us in the pocket. Sugar has nearly doubled in price.

NORTH-SOUTH DIVIDE

The election threatens to expose a north-south cultural divide. Atambayev, from the more Russian-leaning and industrial north, faces challenges from Madumarov and a second candidate who can draw on the nationalism of voters in the poorer south.

Madumarov, a 46-year-old former national billiards champion, wants to reverse the constitutional reforms to give equal prominence to the presidency and parliament.

The other leading southern candidate, trained boxer and former emergencies minister Kamchibek Tashiyev, has said millions would take to the streets to overthrow the country's leaders if they believed the elections to be unfair.

We had a unique chance to hold honest, transparent and secure elections, said another candidate, Marat Imankulov. Unfortunately we haven't seen this. The authorities have thus given a reason for people to express their dissatisfaction.

A representative of the Organisation for Security and Cooperation in Europe's election monitoring arm said earlier that only minor electoral violations had been witnessed in what he called a competitive race.

(There is) the possibility for candidates without impediments to bring their views to the voters, said Douglas Wake, first deputy director of the OSCE's Office for Democratic Institutions and Human Rights.

But he added there had been some challenges with voter lists, with the transparency of the work of the electoral administration.

'KYRGYZSTAN IS DIFFERENT'

In the village of Gulbakhor, home to 3,000 ethnic Kyrgyz in the snowcapped mountains around the main southern city of Osh, residents voted overwhelmingly for Madumarov, who has vowed to spend half his time outside the office if elected president.

He's young and honest, and his pockets are empty. He does not pursue selfish goals, said pensioner Kamchy Aliyev, 82.

But ethnic Uzbeks in the south were voting for Atambayev. Many believe his close ties with Russian Prime Minister Vladimir Putin will protect them from a repeat of the June 2010 ethnic violence in which hundreds were killed.

The next president will be allowed by the current constitution to serve a single 6-year term and will appoint the defence minister and national security head.

The field of 16 candidates and the unpredictability of the result mark Kyrgyzstan out in formerly Soviet Central Asia, a region otherwise governed by authoritarian presidents.

In the context of the region, Kyrgyzstan is different, Walburga Habsburg Douglas, head of the OSCE observation mission, told Reuters. The people have a genuine choice of candidates, who are presenting different programs.

The hopes of many voters were simpler.

May God help our children not to kill and steal from each other, said 62-year-old pensioner Jamillya Karashova. We want peace on our soil. And maybe just a little happiness.

(Additional reporting by Dmitry Solovyov in Osh; Writing by Robin Paxton; Editing by Rosalind Russell)