Former interior minister Mohamed Bazoum, the ruling party's candidate, is the overwhelming favourite to succeed President Mahamadou Issoufou, who is stepping down on Sunday after two five-year terms leading the largely desert country of 23 million.

Bazoum, 60, has promised continuity with Issoufou's policies, while also vowing to clean up pervasive corruption.

"If I am lucky enough to win this election, you will have chosen someone who is ready from day one," he said in a campaign video.

Niger faces twin security crises.

It has suffered repeated attacks near its western borders with Mali and Burkina Faso from militants linked to al Qaeda and Islamic State.

Near its southeastern border with Nigeria it faces attacks from Boko Haram.

Hundreds of soldiers and civilians have been killed in the last year alone.

The economic situation is also critical.

More than 40 per cent of the population lives in extreme poverty and the COVID-19 pandemic has slowed growth to a crawl, compounding the effects of climate change and low prices for top export uranium.

Bazoum faces 29 other candidates, who will hope to force a second round by denying him outright majority.

Hama Amadou, who finished runner-up in the last election, was barred from running because of a criminal conviction, leaving the opposition without an obvious figurehead.

But last week, Amadou's party called on supporters to turn out for Mahamane Ousmame, who was president from 1993-1996.

Australian Associated Press