The United Nations says the closure of borders and airspace in the Niger Republic is cutting off supplies of medicine and food to the landlocked country.

The Niger’s military junta has warned citizens to brace up for challenging weeks and months ahead as soldiers maintain their stance to defend the country against possible attacks.

Part of the defence actions taken by the junta was closing the country’s airspace on Sunday.

Reacting to the decision on Tuesday, Louise Aubin, the UN humanitarian chief in Niger, said any humanitarian cutbacks could have devastating impacts in Niger.

The country has one of highest rates of child mortality in the world while its rural communities have been hit by a deadly Islamist insurgency.

The UN was already set to provide emergency assistance to over four million people before the power grab that ousted President Mohamed Bazoum.

“The risk is that we start running out of assistance materials to be able to help out people – I’m talking about simple things that are so life-saving,” Aubin told Reuters

The UN official listed food, vaccines, and cash as areas of concern.

“The people of Niger are likely to suffer more and so we need to be able to respond very, very strongly,” Aubin added.

Meanwhile, a joint peace mission with representatives of the African Union (AU), the Economic Community of West African States (ECOWAS), and the UN was denied permission to land in Niger by the junta.

Victoria Nuland, United States acting deputy secretary of state, had also been denied permission to meet with coup leader, Abdourahamane Tiani, or with Bazoum, who is in detention.

Instead, she spoke for two hours with other army officers.

“These conversations were extremely frank and at times quite difficult, because, again, we’re pushing for a negotiated solution,” Nuland said.

“They are quite firm in their view of how they want to proceed, and it does not comport with the Constitution of Niger.”