Partial results for Mozambique's high-stakes general election were released on Friday, showing President Filipe Nyusi and his ruling Frelimo party headed for a dominant victory.
The National Electoral Commission (CNE) published the incomplete results as the US embassy in the country said its observers witnessed voting irregularities that it said "strains credulity".
Frelimo, which has ruled the southern African nation for 44 years, had been widely expected to win the presidential, parliamentary and provincial polls held on Tuesday.
But the lopsided nature of partial results published by the National Electoral Commission (CNE) on Friday could revive fears over the country's fragile peace deal.
According to the CNE's running website tally, Nyusi won 75% of the 830 000 votes counted so far - just 6% of the country's 13 million registered voters - in the presidential election.
The candidate of former rebel group turned main opposition party Renamo, Ossufo Momade, had garnered 20%.
In the last presidential election in 2014, Nyusi won 57% over 37% for Afonso Dhlakama, Momade's predecessor.
For the parliamentary election, Frelimo was leading with 70% to Renamo's 22% out of 750 000 votes counted.
Such a crushing win would be a surprise after Frelimo suffered its worst-ever performance at the ballot box last year, winning 51.8% of votes in local elections.
Before the partial results were released, the third biggest party Mozambique Democratic Movement (MDM) slammed the "shameful electoral process".
"We confirm that there has been fraud," the MDM said in a statement on Friday. "These elections were not fair, free or transparent."
Also on Friday, the US embassy in the capital Maputo said its observers witnessed numerous irregularities during the election and early vote counting.
It gave the example of the southern Gaza province, where local observer groups had reported the presence of 300 000 "ghost voters" - names not aligned with real voters - on the electoral roll.
In a campaign marred by violence, perhaps the lowest point came in Gaza, where a prominent election observer was brutally murdered by members of a special police unit.
The US embassy said its teams noted low turnout at numerous Gaza polling station until mid-afternoon, but results posted on Wednesday claimed turnout was close to 100%.
Such results "would have required, in the final hours of the day, a rate of voter processing of such extraordinary alacrity that it strains credulity", the embassy said in a statement.
While the embassy agreed with other international observers that voting had been relatively well-conducted, it noted a "lack of rigour" during the vote counting process.
Frelimo and Renamo signed a peace deal in August hoping to move past a long history of conflict, including a 1975-1992 civil war in which nearly a million people were killed.
As part of the agreement, Frelimo agreed to allow the country's 10 provinces elect governors for the first time.
Renamo had been tipped to win control of between three to five of the provinces, but the one-sided nature of Friday's partial results could cast doubt on that prediction.
The CNE is expected to announce the result of the provincial elections on Monday.
The final results of all the polls must be published within 15 days of the vote.