President Emmanuel Macron said on Friday that France's envoy to Niger is living like a hostage in the French embassy and accused military rulers of blocking food deliveries to the mission.
The ambassador is living off "military rations", Macron told reporters in the eastern town of Semur-en-Auxois.
"As we speak, we have an ambassador and diplomatic staff who are literally being held hostage in the French embassy," he said.
"They are preventing food deliveries," he said, in an apparent reference to Niger's new military rulers. "He is eating military rations."
Niger's military leaders told French ambassador Sylvain Itte he had to leave the country after they overthrew President Mohamed Bazoum on 26 July.
But a 48-hour ultimatum for him to leave, issued in August, passed with him still in place as the French government refused to comply, or to recognise the military regime as legitimate.
The coup has been condemned by France and most of Niger's neighbours.
Macron said the envoy "cannot go out, he is persona non grata and he is being refused food".
Asked whether France would consider bringing him home, Macron said: "I will do whatever we agree with President Bazoum because he is the legitimate authority and I speak with him every day."
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