Who is Nigerien presidential candidate Mahamane Ousmane?

Niger's former president Mahamane Ousmane the underdog in the presidential election on Sunday.

But Ousmane -- 71-years-old -- is giving all he's got in the two-horse race against contender and favourite Mohamed Bazoum who beat Ousmane by 22 points in the first round and is endorsed by the third and fourth-place candidates.

Ousmane was president from 1993-1996 and ousted by a coup.

In his campaign, he has promised to do everything to improve security as attacks by militants linked to al Qaeda and Islamic State intensify.

Ousmane has also criticized the government's record and has pointed to a government audit last year that showed almost 40% of the millions Niger spent on defence contracts in the past three years was lost through inflated costs or material that were not delivered.

Whoever the winner it is a historic election for Niger which has experienced four coups since independence in 1960 and it is the first transition of power between two freely elected presidents.