Opposition parties in Niger said on Tuesday they did not recognise the first partial results from the recent presidential elections after delays amid logistical problems.
The independent National Electoral Commission (CENI) announced the results following polls held on Sunday and Monday.
Provisional results from 20 of the West African country's 308 municipalities gave President Mahamadou Issoufou 40.18 percent of the vote, more than 10 percentage points ahead of his closest rival.
"We cannot recognise them such as they have been proclaimed so far," said Aboubacar Cisse, spokesman for the opposition coalition in response to the result.
Issoufou is seeking a second five-year term. He is popularly known as the "Zaki" or "Lion" in Hausa, the majority language in Niger.
During an interview with AFP last week, the 63-year-old leader said he was "absolutely" confident of a swift victory in the first round of the election.
Authorities in Niger said the results should be announced within five days of the close of voting.
A total of 7.5 million Nigerien were eligible to vote across the country on the edge of the Sahara desert, where security is a growing concern after attacks by Boko Haram in neighbouring Nigeria and Al-Qaeda affiliated groups in Mali and Libya.