OUAGADOUGOU (AFP) - Hundreds of thousands of voters in Burkina Faso were unable to cast ballots in Sunday's (Nov 22) general election due to security threats, officials said, as the West African nation grapples with a growing Islamist insurgency.

An undisclosed number of troops were deployed for the presidential and parliamentary polls, which are widely expected to see President Roch Marc Christian Kabore re-elected.

But no votes were cast in one-fifth of the country, where large swathes of territory remain outside the state's control and extremists strike almost daily.

The Electoral Commission reported that a "certain number" of polling stations for the presidential vote had been closed after threats were made against them.

Commission president Newton Ahmed Barry later told reporters that between 300,000 and 350,000 of about 6.5 million voters had not cast their ballots due to "security threats".

Islamist-related violence has forced one million people - five per cent of the 20 million population - from their homes in the last two years and at least 1,200 have been killed since 2015.

The security crisis - inflamed by the presence of the regional offshoots of Al-Qaeda and the Islamic State in Iraq and Syria (ISIS) group - dominated the campaign in the landlocked West African country, one of the world's poorest.

Most of the 12 opposition candidates running against Mr Kabore have criticised the incumbent's failure to stem the bloodshed.

"I hope for a lot of good things for the country: first a president who will be up to the security situation and also deputies who will vote for laws to bring us development," said Ouagadougou resident Christian Koula after voting in the capital.

On Sunday morning, after voting in his district of Ouagadougou, Mr Kabore rejected opposition accusations of fraud at the ballot box.

"Controversies are for another day. Now we vote," he said.

But political scientist Drissa Traore said Mr Kabore remains "the big favourite against an opposition which has not managed to unite behind a single candidate".

'Massive fraud'

Mr Kabore's two main challengers are 2015 runner-up and veteran opposition leader Zephirin Diabre, and Mr Eddie Komboigo, standing for the party of former president Blaise Compaore.

Mr Compaore, who was ousted by a popular uprising in 2014 after 27 years in power, is now in exile, but some voters are nostalgic for his regime.

Mr Diabre told reporters on Saturday that "there is a huge operation orchestrated by those in power to carry out a massive fraud" so as to give Mr Kabore a first-round victory.

"We will not accept results marred by irregularity," added Mr Diabre, surrounded at a press conference by five of the other 11 opposition candidates, including Mr Komboigo.

The head of the President's party, Mr Simon Compaore, rejected Mr Diabre's "allegations".

Mr Kabore did not need "any kind of fraud to win the elections", he said.

Mr Kabore can avoid a run-off by winning more than 50 per cent of the vote in Sunday's first round - as he did in the last election in 2015.

Campaigning and bloodshed

The campaigning ran alongside continued bloodshed and the fear of Islamist attacks on voting day was high.

Fourteen soldiers were killed in an ambush in the north claimed by ISIS earlier this month, one of the deadliest attacks on the military in the five-year insurgency.

Days later, the ISIS propaganda arm published a picture of two extremists killing a man wearing an army uniform - but the military denied there had been a new attack.

Islamist violence in the north - as in the neighbouring Sahel states Mali and Niger - has become intertwined with clashes between ethnic groups.

Almost all of Mr Kabore's challengers have called for dialogue with the extremists to be explored - a suggestion Mr Kabore has emphatically rejected.