The electoral commission in Niger says the ruling party’s candidate Mohamed Bazoum has won the presidential election with more than 55% of the vote.
His opponent, former president Mahamane Ousmane, alleged fraud as his supporters burned tyres in the streets.
This is Niger’s first transition from one democratically elected leader to another, with President Mahamadou Issoufou stepping down after two five-year terms.
Mr Bazoum is a former interior minister and close ally of Mr Issoufou.
Niger, which is the world’s poorest country, is struggling to contain an Islamist insurgency.