The Gambia's President Yahya Jammeh has won a fourth term in office in Thursday's election, taking 72% of the vote, the election commission has said.
Electoral chairman Mustapha Carayol said voter turnout had been 83%.
Opposition candidates Ousainou Darboe and Hamat Bah took 17% and 11% respectively, he said.
But Mr Darboe called the results "bogus, fraudulent and preposterous" and he urged the international community not to accept them.
"[They] constitute a capricious deception of the will of the people," the United Democratic Party leader said.
Ahead of the poll, the West African regional body Ecowas said the vote would not be free or fair because of intimidation by the governing party.
The 15-nation bloc said its investigations found "an opposition and electorate cowed by repression and intimidation" and it refused to send election observers to the tiny West African country.
But observers from the African Union (AU), Commonwealth and the Organisation of Islamic Co-operation (OIC) did monitor the poll.
These groups said there may have been some problems leading up to the campaign, but the election period itself was credible, the BBC's Umaru Fofana reports from Gambia's biggest town Serrekunda, near the capital, Banjul.
He says Mr Jammeh's supporters from the governing Alliance for Patriotic Reorientation and Construction party, wearing green T-shirts and waving mango tree leaves, can be seen celebrating in Serrekunda. Others are driving through the streets honking their horns.
Mr Jammeh, who came to power in a bloodless coup 17 years ago, has a bigger mandate than in 2006 when he won 67% of the vote in polls widely criticised by observers.
In that election, Mr Darboe secured 27% of the vote and turnout was about 59%.
After he cast his vote on Thursday, Mr Jammeh said he was in no doubt that he would win.
"In 17 years, I have delivered more development than the British were able to deliver in 400 years," he told the BBC.
"Do I look like a loser? There is no way I can lose unless you tell me that all Gambian people are mad," he said.
Mr Jammeh's government has been criticised by international rights groups for its attitude to civil liberties, especially freedom of the press and the detention and disappearance of journalists.
In response to such criticism, he said on Thursday: "The journalists are less than 1% of the population and if anybody expects me to allow less than 1% of the population to destroy 99% of the population, you are in the wrong place."