The US has expressed concern over "inconsistencies" in preliminary results of Guinea's presidential election.

In a statement, the US embassy spoke of a "lack of transparency in vote tabulations and inconsistencies between the announced results and tally sheets results from polling stations".

Guinea's 82-year-old leader Alpha Condé won a controversial third term in office, according to preliminary results, amid violent protests across the country.

The US has urged all parties to peacefully resolve electoral disputes through established institutions. It said it supported diplomatic efforts by the West African regional bloc, Ecowas, the African Unions and the UN.

The main opposition leader, Cellou Dalein Diallo, had declared himself winner and was prevented from leaving his house until Wednesday when he said the security officers outside his home had been withdrawn.