Guinea's Supreme Court has validated results showing a landslide election win for coup leader Mamady Doumbouya, clearing the way for the former special forces commander to serve a seven-year term as president.

The court also said late on Sunday the second-place finisher, Abdoulaye Yero Balde, had dropped his legal challenge to the result, which was condemned by opposition supporters online. Balde did not immediately respond to requests for comment.

Doumbouya, thought to be in his early 40s, seized power in Guinea, a West African nation rich in bauxite and iron ore, in a 2021 coup, toppling then-president Alpha Conde. On New Year's Eve, Conde gave a speech dismissing the vote as a "masquerade".

The court's validation, required after every vote, confirmed provisional results that said Doumbouya had secured 86.72% of the vote in the December 28 election against a fragmented field of eight challengers.

In a short speech after the ruling, Doumbouya called on "all the daughters and sons of our nation, both here and in the diaspora, to come together to build a new Guinea". 

The results showed Balde, the leader of the opposition Democratic Front of Guinea, came in second with 6.59% of the vote.

He had asked the Supreme Court to annul the provisional results, saying the vote count was not transparent and that representatives of his party had been expelled from some polling stations. 

The US embassy in Guinea congratulated Doumbouya and said Washington was looking forward to strengthening ties and advancing economic stability.