The airspace was closed by the junta on Sunday "in the face of the threat of intervention that is becoming more apparent," a representative said in a statement on national television.

He said there had been a pre-deployment of forces in two Central African countries in preparation for an intervention - but did not give details.

Thousands of junta supporters flocked to a stadium in the capital Niamey, cheering the decision not to cave in to external pressure to stand down by Sunday following the power grab on 26 July.

Prior to Sunday's deadline, defence chiefs of the West African regional body - known as ECOWAS, agreed a possible military action plan, including when and where to strike, if the detained president Mohamed Bazoum was not released and reinstated by Sunday.

ECOWAS has said it will hold a summit in Nigeria's capital Abuja on Thursday to discuss the coup in Niger.

Mr Bazoum, who has claimed he is a "hostage", was elected two years ago in the nation's first peaceful, democratic transfer of power since its independence from France in 1960.

He had been seen as a key Western ally in the region in the fight against extremists linked to al Qaeda and Islamic State.

The coup, led by General Abdourahmane Tchiani, marked the seventh in West and Central Africa since 2020.

ECOWAS sanctions have led to power cuts and soaring food prices but it was not immediately clear what the bloc will do next as it faces prominent calls to pursue more peaceful means.

An escalation in the stand-off with ECOWAS would further destabilise the region and the bloc's military threat has triggered fears of further conflict in a region already battling the deadly Islamist insurgency that has killed thousands and forced millions to flee.

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Any military intervention could be complicated by a promise from juntas in neighbouring Mali and Burkina Faso to come to Niger's defence if needed.

Given its uranium and oil riches and its pivotal role in a war with Islamist militants, Niger holds importance for China and Russia.

It is also a security ally of France and the US, which both use it as a base to fight an Islamist insurgency in West and Central Africa's wider Sahel region.