The walls of Burkina Faso's capital Ouagadougou are smothered in posters as more than a dozen rivals try to win over voters ahead of Sunday's general election.

But one colour -- orange -- dominates.

It's the campaign colour of President Roch Marc Christian Kabore, who is running for a second term, defying criticism of his failure to blunt a jihadist insurgency.

Kabore, 63, is the big favourite in Sunday's presidential election.

His supporters are hoping for an outright victory in the first round, obviating the need for a runoff vote.

But in the West African country's most open elections in years, Kabore faces a stiff challenge from Zephirin Diabre, the runner-up in 2015's election, and Eddie Komboigo, standing for the party of former president Blaise Compaore, who was ousted in a popular uprising in 2014.

Burkina Faso's security crisis has dominated the campaign. Kabore has relied on the military to fight the threat, but some are now saying that dialogue with the jihadists should be explored.

Located in the heart of the Sahel, this impoverished country of some 20 million people is in the fifth year of a crisis that has claimed more than 1,200 lives and forced a million people from their homes.

"The priority is peace, that's the first thing that the next president should deal with," Marcelin Sandwidi, a 30-year-old Diabre supporter sporting the candidate's yellow and green on his cap, said at an opposition rally in Ouagadougou on Sunday.

But Kabore's supporters say he has a long-term plan for combatting the jihadists -- and now is not the time to rock the boat.

"Only Roch can respond and win the war," said orange-clad Barry Amadou.

- Struggling army -

Kabore is focusing on a military solution to the crisis, hoping that a civilian auxiliary militia created last year called the Volunteers for the Defence of the Nation will provide a vital push.

But the poorly equipped and disorganised army is flailing, analysts say.

Kabore's strategy "has not radically changed" over the years, a western diplomatic source told AFP.

Despite frequent claims of success, it depends on France's Barkhane anti-jihad mission in the Sahel, a reliance that is a source of political discomfort for the government.

Almost every week brings grim news of military losses.

In the latest attack, 14 soldiers were killed last week in an ambush at Tin Akoff, near the border with Niger.

Most candidates called a 48-hour suspension in their campaign to mourn the dead.

Swathes of Burkina Faso remain outside the state's control.

Voters in nearly 1,500 out of 8,000 villages -- amounting to 17.7 percent of the country's area -- will be unable to cast their ballot in Sunday's presidential and parliamentary elections.

- Talk to jihadists? -

Jihadism expert Mahamoudou Savadogo said that under Kabore there has been a "denial of seeing the reality of the problem."

"Realisation (of the problem) came too late, and the response has been ill-matched and inadequate."

The idea of talking to the jihadists in the Sahel, some link