Supporters of losing candidate Mahamane Ousmane have turned to the streets since Tuesday. Police said 468 were arrested.
At least two people were killed as supporters of the losing candidate in Niger's presidential elections led violent protests in the capital Niamey, Interior Minister Alkache Alhada said on Thursday.
The opposition runner Mahamane Ousmane has deemed the elections fraudulent after the electoral commission announced the ruling party candidate Mohamed Bazoum's win.
"The toll is two dead," Alhada told reporters, adding that police arrested 468 protesters since Tuesday.
Alhada accused the opposition figure Hama Amadou of inciting the violence.
"(He) is being sought and as usual he is on the run, but we will find him," Alhada added.
Houses set on fire
Ousmane's supporters have marched since Tuesday, throwing rocks at police, who fired tear gas to disperse them.
Some protesters set buildings on fire. Radio France International (RFI) said that its correspondent Moussa Kaka's house was among those set on fire.
RFI said that Kaka's family was safe and described the attack as "a grave attack on freedom of the press."
Kaka had spent months in prison between 2007 to 2008 on charges of "endangering state security" after authorities accused him of ties with Tuareg rebels in northern Niger.
Ousmane claims winning
Ousmane was the first democratically elected president in Niger. He served from 1993 until a military coup toppled him in 1996. He has since tried to regain power five times.
Bazoum was the interior minister and outgoing President Mahamadou Issoufou's right-hand man. The electoral commission announced his win with 55.75%, but Ousmane claimed that he was the winner with 50.3%.
An observer mission from the Economic Community of West African States contended Ousmane's claim, saying that the elections were held "under free, fair, credible and transparent conditions," according to AFP.
Violence plagues Niger
On Sunday, people cast the ballot for Niger's first-ever democratic transition of power.
Seven members of the National Electoral commission were killed on the same day after their car hit an explosive device.
The country struggles with jihadist insurgencies from its southeast neighbor Nigeria and Mali in the west.
Extremists attacked two villages near Niger's border with Mali, killing more than 100 people in January.
Niger is listed as the world's poorest nation on the UN's development rankings for 189 countries.
The west-African country has had four coups since its independence from France in 1960.