West Africa's chief mediator in the Niger crisis, ex-Nigerian military leader Gen Abdulsalami Abubakar, has told the BBC that military intervention remains the last option to resolve the situation in the country.

He said his delegation from the regional grouping Ecowas has started negotiating with military junta leader Gen Abdourahmane Tchiani and expressed hope for an amicable resolution.

Gen Tchiani announced a three-year transition plan at the weekend, which Ecowas has rejected.

West Africa remains on edge as the junta leader remains defiant despite the threat of military intervention.

While Ecowas insists that all options remain open, the junta’s announcement of a three-year-long return to civilian rule has left regional leaders in a dilemma on how to respond.

But Gen Abubakar told the BBC that his recent mission to Niger has "opened a room for discussion and diplomacy".

Referring to the use of force, he said that "all measures will be put in place to ensure that Niger comes back to constitutional authority... It doesn't necessarily mean going to war however, nobody is planning or hoping to go to war because when you start war, you don't know the outcome."

Gen Abubakar also met the ousted President, Mohamed Bazoum.

The president "made a lot of complaints about the way he has been treated, we have confirmed that they have cut off light (electricity) to him and they are keeping him in custody," Gen Abubakar said.

"He was naturally very bitter about the way he has been treated and he claims he is being kept a prisoner for no reason at all."

The Nigerian former leader also said that Ecowas sanctions were having a serious impact on Niger and were causing great hostility towards the regional bloc.