Niger’s airspace closed on Sunday, the day imposed as a deadline by a group of African countries for Nigerien military coup leaders to release power and reinstate the country’s democratically-elected president, CNN reported.

As that deadline expired, Niger’s airspace closed due to “the threat of intervention from neighboring countries,” according to a video statement by Nigerien coup leader Colonel Major Amadou Abdramane.

The military coup in Niger was launched late July. President Mohamed Bazoum was seized by members of the presidential guard, national institutions were shut down and protesters from both sides eventually took to the streets, including thousands who support the military coup.

But outside Niger, the coup leaders’ actions were quickly condemned by the United States and some Western nations, as well as group of western African countries, which threatened force.

The Economic Community of West African States (ECOWAS), a regional bloc, warned that if the military junta does not stand down, it could face possible military intervention and gave coup leaders until Sunday to cede power.

Should the junta remain in charge, the group has said it would “take all measures necessary to restore constitutional order,” including using force.