By Layli Foroudi and Zhifan Liu
PARIS (Reuters) - France began the evacuation of hundreds of French and European citizens from Niger on Tuesday, a day after neighbours Mali and Burkina Faso said any outside intervention to restore the ousted government would be seen as a declaration of war.
A military junta overthrew Niger's democratically elected President Mohamed Bazoum and his government last Wednesday in the seventh military takeover in less than three years in West and Central Africa.
The coup has sent shockwaves across West Africa's Sahel region, one of the poorest and most unstable in the world, where Niger was considered the West's most stable ally in the fight against a fast-growing Islamist insurgency.
West African regional bloc ECOWAS has threatened to use force to reinstate Bazoum, while neighbouring Mali and Burkina Faso - also ruled by military juntas - said they would come to Niger's defence.
With the risk of conflict escalating, Spain said it was preparing to evacuate more than 70 citizens by air and Italy said it would organise a repatriation flight. Germany urged its citizens to join the French flights.
The recent coups in the region have come amid a wave of vitriol aimed at former colonial power France that resulted in its troops being kicked out of Mali and Burkina Faso this year and last. Many of those soldiers are now stationed in Niger.
The United States, Germany, and Italy also have troops in Niger on counter-insurgency and training missions. There has been no announcement of troops being evacuated so far.
Niger's new military leaders have arrested senior politicians and warned against any foreign attempts to extract Bazoum, who is still shut in his palace.
"Considering the ongoing coup in Niger and the fact that the situation continues to be worrying, we decided to make sure that the French citizens who want to leave Niger can do so," French Foreign Minister Catherine Colonna told France's LCI TV.
She estimated that hundreds of French citizens and hundreds of other EU citizens wanted to be evacuated on flights she hoped would be completed over 24 hours.
Flightradar showed a plane registered to the French armed forces left the airport of the capital Niamey on Tuesday evening. Earlier, a crowd of expats gathered outside the terminal with their suitcases, photos shared with Reuters showed.
"I never thought we would leave like this," said a French woman who was waiting to depart with her family and sent messages to Reuters by phone.
"It's a scene worthy of a war movie."
'DECLARATION OF WAR'
West African bloc ECOWAS has taken its hardest line yet on Niger, after struggling to persuade the military rulers of member states Mali, Burkina Faso and Guinea to restore democracy.
A declaration by Mali and Burkina Faso on Monday night suggested a new alliance may be forming in opposition to the rest of the 15-member-state bloc.
"Mali and Burkina Faso warn that any military intervention in Niger will be considered as a declaration of war against Burkina Faso and Mali," said a joint statement read on both countries' national broadcasters.
They said that they would withdraw from ECOWAS and adopt "measures of legitimate defence" to support Niger's army and people if ECOWAS intervened. Guinea's military leaders also expressed solidarity with Niger.
It is not clear what help Mali and Burkina Faso would provide, given that their under-equipped armies are already failing to contain domestic Islamist insurgencies that have killed thousands.
Yevgeny Prigozhin, the head of Russia's Wagner mercenary group which operates in Mali, last week welcomed the coup in Niger, and said his forces were available to restore order.
The Kremlin called for a swift return to constitutional order.
Niger is the world's seventh-biggest producer of uranium, the radioactive metal widely used for nuclear energy and treating cancer.