Niger's coup leaders on Monday closed its airspace after an ultimatum from the Economic Community of West African States to reinstate elected President Mohamed Bazoum expired on Sunday night.
The military junta calling itself the National Council for the Safeguarding of the Fatherland seized power on July 26 and detained Bazoum, with the commander of the country's presidential guard, General Abdourahmane Tchiani, proclaiming himself the country's new leader.
The coup was widely condemned by the international community, including the U.S., the European Union, Russia and former colonial power France, along with Nigerian-led regional body ECOWAS, which also sanctioned the junta.
Many foreign countries have already begun evacuating embassy staff and citizens from Niger, while the likes of the U.S. and U.K. have partially suspended aid programs.
The 15-member ECOWAS gave the military junta one week to return the elected government to power and restore constitutional order, threatening the use of force if its demands were not heeded.
As the Sunday night deadline loomed, thousands of Nigeriens gathered at a stadium in the capital Niamey to show support for the coup leaders, while rallying against France and other Western powers and voicing admiration for Russia.
In a statement on national television on Sunday, a spokesman for the Niger junta repeated claims that a "foreign power" was preparing military intervention, and said the country's military stands ready to respond.
ECOWAS defence chiefs met late last week to draw up plans for a possible military response, and Abdel-Fatau Musah, commissioner for political affairs, peace and security, said on Friday that the bloc's heads of state will make a final decision.
"All the elements that will go into any eventual intervention have been worked out here, including the resources needed, the how and when we are going to deploy the force," Musah said at the close of the three-day meeting in Abuja, Nigeria.
Nigerian President Bola Tinubu, who also serves as chair of ECOWAS, sent a letter to the senate on Friday, asking members to back a regional intervention in the neighboring country, according to local media reports.
There were no aircrafts seen over Nigerien airspace on Monday, according to FlightRadar24, which said in a blog post that flights already in the air when the airspace closed were rerouted or diverted. It added that the no-fly order is likely to be extended beyond the initial Monday night expiry.
"The closure of Niger's airspace dramatically widens the area over which most commercial flights between Europe and southern Africa cannot fly. Flights must already take a detour of sorts around Libya and Sudan," the flight tracker said.