Opposition candidates in Mauritania's presidential election on Sunday cried foul after government candidate Mohamed Cheikh El-Ghazouani claimed victory before full results were in.
Sidi Mohamed Ould Boubacar, addressing a news conference along with three other candidates, said "multiple irregularities... eliminated any credibility" of the Saturday polls in the West African desert nation.
"We reject the results of the election and we consider that they in no way express the will of the Mauritanian people," he said, vowing that the opposition would use "every legal means" to challenge them.
The electoral commission earlier Sunday issued results showing that Ghazouani won an absolute majority in the first round with counting completed in 3,729 of a total of 3,861 polling stations.
According to data published on the Independent National Electoral Commission (CENI) website, the 62-year-old former head of the domestic security service won 51.5 percent of the vote.
If the result is confirmed, Ghazouani will have won outright, with no need to contest a second-round runoff.
Ghazouani had already declared himself the winner in the early hours of Sunday in the presence of outgoing president Mohamed Ould Abdel Aziz, his supporters and journalists.
Another candidate, Biram Ould Dah Ould Abeid, told the news conference: "We are launching an appeal to the Mauritanian people... to resist, within the bounds of the law, this umpteenth coup d'etat against the will of the people."
Although this ballot is the first in Mauritania's coup-strewn history that looks set to see an elected president complete his mandate and transfer power to an elected successor, the opposition has raised concerns that the vote could perpetuate a government dominated by military figures.
Some 1.5 million people were eligible to vote in the vast predominantly Muslim state, which is approximately twice the size of former colonial power France but has a population of just 4.5 million.
Turnout was 62.68 percent, CENI said.
Abeid came second with 18.58 percent of the votes and Boubacar followed in third place with 17.82 percent, the CENI data showed.
CENI said in a statement that it would continue compiling the results before handing them over to the Constitutional Council.
In the meantime, it said it "advises the candidates to show prudence and restraint", and hoped the calm during the campaign and on voting day would prevail.
Both Abeid and Boubacar had complained of balloting irregularities and the expulsion of representatives from some polling stations. However CENI said no major problems had been reported.
Ghazouani -- who campaigned on the themes of continuity, solidarity and security -- served as Abdel Aziz's chief of staff from 2008 to last year.
The outgoing president is a general who originally came to power in a 2008 coup, won elections a year later and was again elected in 2014 in polls boycotted by the opposition.
Abdel Aziz has repeatedly warned that the country could fall back into instability if his chosen candidate is not elected. He is credited with reforming the army, clamping down on jihadists and pushing to develop remote regions.
Nevertheless, rights groups have accused the government of restrictions on freedom of expression and assembly, while calling on the nation to do more to counter violence against women and slavery, which persists in this deeply conservative state, even though it was officially abolished in 1981.
Authorities rejected an opposition request for foreign observers at the election.
All of the candidates promised improvements in the standard of living, though economic growth at 3.6 percent in 2018 is insufficient to meet the needs of a fast-growing population, according to the World Bank.
The World Bank has welcomed the "macro-economic stabilisation" of the country, where annual growth is expected to average 6.2 percent between 2019 and 2021.
But it has called for barriers to be removed in the private sector, pointing in particular to corruption, as well as difficult access to credit.