The French foreign ministry on Wednesday issued a firm warning against travelling to Niger after six French nationals were among eight people killed by suspected jihadists at the weekend.
The ministry website said people were "strongly advised" not to travel anywhere in the country, the exception being the capital Niamey, for which travel was "not advised unless for compelling reasons."
The new advice means that the southern part of Niger, roughly a quarter of the country, has been added to the so-called red zone, for which there is a strong recommendation to avoid.
"The terrorist threat against Niger, especially outside the capital and near the borders, is very high," the ministry said.
The impoverished country lies in the heart of the Sahel, which has become badly destabilised by a jihadist insurgency that began in northeastern Nigeria in 2010 and in Mali in 2012.
Six French aid workers, their Nigerien guide and a driver were murdered on Sunday in the Koure National Park, a wildlife haven 60 kilometres (37 miles) from the capital Niamey.
The killings were the first by jihadist gunmen in that area, a destination for weekend leisure trips by Niamey residents, including foreigners.
Previously, Niamey and the town of Koure were marked as yellow under France's colour-coded security advice -- a category that calls for additional vigilance but says the risk is "compatible with tourism."
Niamey is now classified as orange (travel "not advised unless for compelling reasons") while Koure, like the rest of the country, is in the red zone.