The French foreign ministry says it will soon start evacuating its nationals in Niger following a coup last week.

It said that amid the deteriorating security situation, evacuations by air were being prepared and "will take place very soon in a very limited span of time," the AFP quoted a message sent out by the French embassy in Niamey.

Niger President Mohamed Bazoum was overthrown last week by troops from his presidential guard after they seized power.

It is the third country in the Sahel, after Burkina Faso and Mali, to experience a coup in less than three years.

The incidents have been accompanied by anti-French sentiment, with the countries embracing ties with Russia.