Niger's military junta closed the country's airspace and accused foreign powers of planning an invasion, as it defied an ultimatum to reinstate the ousted president.

The mutinous soldiers warned Monday that any attempt to fly over the country will be met with "an energetic and immediate response."

Niger's state television announced the move Sunday night, hours before a deadline set by the West African regional bloc ECOWAS, which demanded the coup leaders reinstate President Mohamed Bazoum or face military force.

A spokesman for the coup leaders, Col. Maj. Amadou Abdramane, warned of "the threat of intervention being prepared in a neighboring country," and said Niger's airspace will be closed until further notice.

The junta asserted that two central African countries are preparing for an invasion, but did not say which ones, and called on the country's population to defend it.

International airlines diverted flights around Nigerien airspace Sunday.

Regional tensions have mounted since mutinous soldiers overthrew Niger's democratically elected president nearly two weeks ago, detaining him and installing Gen. Abdourahmane Tchiani as head of state. Tchiani was head of the presidential guard, and is accused of leading the coup with several members of his unit.

Analysts say the coup is believed to have been triggered by a power struggle between him and the president, who was about to fire him. While some experts painted a broader picture of a battle for influence between the West and Russia.

It was not immediately clear what ECOWAS will do now that the deadline has passed, especially because the region is divided on a course of action.

On Saturday, Nigeria's Senate pushed back on the plan to invade, urging Nigeria's president, the bloc's current chair, to explore options other than the use of force. ECOWAS can still move ahead, as final decisions are made by consensus by member states.

Regional countries Guinea, Burkina Faso and Mali, as well as Algeria, have come out against the use of force, with Burkina Faso and Mali saying an attack on Niger "would be tantamount to a declaration of war" against them.

Senegal and Ivory Coast have both expressed support for ECOWAS' efforts to restore constitutional order, and Senegal's government said it would participate in a military operation if it went ahead.

A former British military officer who worked in Nigeria said military officials there told him Monday that President Bolu Tinubu had not given orders to use military force. He spoke on condition of anonymity because of the sensitivity of the situation.

But the junta does not appear interested in negotiation.

An ECOWAS delegation sent to Niger last week for talks was not allowed to leave the airport and met only representatives of Tchiani.

On Sunday, junta leaders appeared at a rally in the capital, Niamey promising the thousands of supporters present that their loyalty will not be betrayed.

"We are with you against them. We will give you the Niger that you are owed," said junta member Brig. Gen. Mohamed Toumba. After his speech, The Associated Press saw rallygoers behead a chicken decorated in the colors of former colonizer France.

The junta is exploiting anti-French sentiments among the population to shore up its support base and moving swiftly to cut ties with France, which French soldiers worked with the Nigerien military to fight terrorist groups while looking to other partners.

Last week the junta also suspended French broadcaster RFI and France 24 television from operating in the country and severed accords with France. French soldiers have been working with the Nigerien military to fight terrorist groups.

It also asked for help from the Russian mercenary group Wagner, which operates in a handful of African countries including neighboring Mali, which is also run by a military regime.

On Monday, France's ministry of foreign affairs "formally discouraged" any travel to Niger, Burkina Faso or Mali, and called on French nationals to be extremely vigilant.

Niger had been seen by the United States, France and other countries as their last major counterterrorism partner in the vast Sahel region, south of the Sahara Desert, where groups linked to al-Qaida and the Daesh terrorist groups have been expanding their influence. The future of some 1,500 French military personnel and 1,100 U.S. military personnel in Niger is not immediately known.

Many people, largely youth, have rallied around the junta, taking to the streets at night to patrol, check cars for weapons and stand guard against foreign intervention.

"I am here to support our defense and security forces of my country," said a coup supporter at the rally Sunday. "While they (terrorists) kill our brothers and sisters ... Ecowas didn't intervene. Is it now that they will intervene?" said Amadou Boukari supporter at the rally Sunday. "Shame on Ecowas."

But others have expressed concerns about the junta's tightening grip on the population.

One official, who spoke on condition of anonymity because they were not authorized to comment, said the junta is scaring people into joining them and has people informing them about which Nigeriens speak with foreigners.