The Gambia's President Yahya Jammeh is about to concede defeat, the electoral commission chairman has told the BBC.

Mr Jammeh, who has been in power for 22 years, faced estate agent Adama Barrow in Thursday's election.

Electoral commission chief Alieu Momar Njie said it was unprecedented for a Gambian head of state to accept defeat before the final results.

The West African country has not had a smooth transfer of power since independence in 1965.

There has been no official word from Mr Jammeh, who took power in a coup in 1994.

The 51-year-old leader has been trailing Mr Barrow in partial results and was defeated in the capital, Banjul, his stronghold.

A devout Muslim, Mr Jammeh once said he would rule for "one billion years" if "Allah willed it".

"It's really unique that someone who has been ruling this country for so long has accepted defeat," Mr Njie told reporters.

Image copyright Reuters

Image caption Adama Barrow has proved popular with younger voters

During the campaign, the country's mostly young population seemed to be yearning for change, said the BBC's Umaru Fofana in Banjul.

The economic challenges the country faces have forced many to make the perilous journey to Europe, with some drowning on the way, he said.

Human rights groups have accused Mr Jammeh, who has in the past claimed he can cure Aids and infertility, of repression and abuses.

Several previous opposition leaders are in jail after taking part in a rare protest in April.

Observers from the European Union (EU) and the West African regional bloc Ecowas did not attend the vote.

Gambian officials opposed the presence of Western observers, but the EU said it was staying away out of concern about the fairness of the voting process.

The African Union did despatch a handful of observers to supervise the vote, however.

The Gambia, a tiny country with a population of fewer than two million, is surrounded on three sides by Senegal and has a short Atlantic coastline popular with European tourists.