Paul Biya has ruled Cameroon for 29 years [GALLO/GETTY]

Two military policemen were killed in the unstable southwestern Bakassi region of Cameroon while securing presidential elections there, the government has said.

They were killed on Sunday by "armed men who have not yet been identified" in Isanguele district, Marafa Hamidu Yaya, the interior minister, told reporters as votes were being counted across the country.

"These brave elements of our security forces were on a mission to secure the electoral process," the minister said. "All steps are being taken to find and apprehend their killers."

Several groups, often armed, operate in the coastal Bakassi peninsula, carrying out assaults and kidnappings the authorities blame on pirates.

About seven million Cameroonians were eligible to vote for a president on Sunday with incumbent Paul Biya almost assured of extending his 29-year rule amid signs of apathy in a ballot the opposition termed a "mess".

Earlier in the day, voters faced delays and organisational shortfalls in parts of the country.

Biya, 78, is viewed as keeping his place among the clutch of African leaders in power for decades. And rivals had alleged the vote was skewed against them.

There were no official turnout figures but voting appeared sluggish in the capital Yaounde.

Foregone conclusion

Many Cameroonians appeared indifferent to the election campaign, feeling the vote was a foregone conclusion.

Results could take days to emerge.

Election observers said voting was peaceful but cited delays at some polling stations and irregularities such as some voters being allowed to jump the queue.

After voting ended, a Reuters reporter in Yaounde saw 19 polling stations where ballots were being counted without the required presence of candidates' representatives.

"Some polling stations opened late, some appeared unclear on the rules about how votes are cast," Commonwealth observer mission leader Frederick Mitchell said by telephone.

Biya's main rival, John Fru Ndi of the Social Democratic Front (SDF), said a surplus of voting slips meant some had voted twice in certain parts of the country and said election body Elecam would be blamed for the "disorder and confusion".

Casting his vote in Yaounde, Biya asked for patience.  "It [Elecam] is a young organisation ... I'm just asking
that there should be indulgence in any eventual imperfection. There was no intention to fraud," he said.

Biya faces 22 candidates including Fru Ndi, and Adamou Ndam Njoya of the Cameroon Democratic Union (UDC).

In the last election in 2004, Biya scored just over 70 per cent, while his closest rival Ndi took 17 per cent.