American military commanders were dismayed last month when a clique of top army officers seized power in Niger, the U.S.’s main ally in the fight against Islamist militants in West Africa.

Niger military leaders, who have recently overthrown the elected government of President Mohamed Bazoum, have denied U.S. Acting Deputy Secretary of State Victoria Nuland a meeting with the ousted leader.

"We asked before we arrived and throughout the day for an opportunity to meet with President Bazoum to get his perspective directly – we've talked to him on the phone, but we haven't seen him – and that was never granted," Nuland said at the U.S. state department's press briefing.

Russia's Wagner mercenary group is "taking advantage" of instability in Niger, US Secretary of State Antony Blinken has told the BBC.

The country has been ruled by a junta following the ousting of President Mohamed Bazoum nearly two weeks ago.

There have been suggestions the coup leaders have asked for help from Wagner, which is known to be present in neighbouring Mali.

Mr Blinken said he did not think Russia or Wagner instigated Niger's coup.

Niger's coup leaders have closed the country's airspace until further notice, citing the threat of military intervention from their neighbours.

It comes after the Ecowas group of West African states demanded President Mohamed Bazoum be reinstated by Sunday.

Ecowas had warned that the junta could face military action and will now meet on Thursday to discuss next steps.

Meanwhile Mali and Burkina Faso, both also ruled by juntas, said they would send officials to Niger in solidarity.

West Africa is on the brink of armed conflict as a regional security bloc must decide whether to intervene against the junta leaders in Niger, at least one of whom previously trained under Department of Defense (DOD) programs.

Airlines were forced to divert some flights after Niger restricted its airspace on Sunday night, making it more difficult for planes to fly across parts of Africa.

British Airways was one of the carriers affected by Niger’s partial closure of airspace, with at least five flights to and from its London hubs diverting — including services from Nairobi, Cape Town and flights to and from Johannesburg. Air France, KLM and Deutsche Lufthansa AG also saw services diverted or delayed.

Coup leaders in Niger have closed the country's airspace and have brought in reinforcements after the West African group of countries, Ecowas, warned it could use force if President Mohamed Bazoum was not reinstated

Bazoum was detained on July 26, and Gen Abdourahmane Tchiani, commander of the presidential guard, proclaimed himself the new leader, sparking condemnation from leaders from Africa, France, the European Union and the United States.

The deadline arrived Sunday for Niger’s military junta to reinstate the country’s ousted president, but the West Africa regional bloc that has threatened a military intervention faces prominent appeals to pursue more peaceful means. In the capital, coup leaders appeared at a stadium rally where a chicken decorated in the colors of former colonizer France was beheaded, to cheers.

Niger’s president hid behind a bulletproof door of his official residence and talked over a phone he assumed was monitored. To anxious French and American allies, he repeated assurances that the army would soon rescue him from an unfolding coup. 

U.S. President Joe Biden on Thursday called for the immediate release of Niger's democratically elected head-of-state amid an apparent coup there.

Biden released the statement on the 63rd anniversary of Niger's independence from its former colonial ruler, warning that the West African nation is now "facing a grave challenge to its democracy."