France pledged Tuesday to ramp up security for its nationals in the Sahel region following an attack in Niger at the weekend in which eight people, six of them French, were murdered by jihadists.
"I've decided to boost security measures for our expatriates in the region," French President Emmanuel Macron tweeted after a cabinet meeting on what he described as "manifestly a terrorist attack".
Macron did not elaborate on the exact nature of the measures envisaged.
Seven of the victims worked for the French humanitarian NGO, Acted.
They were attacked Sunday in Koure National Park, just 60 kilometres (37 miles) from the Nigerien capital of Niamey.
The killings were the first by jihadist gunmen in that area, a destination for weekend leisure trips by Niamey residents, including foreigners.
French Prime Minister Jean Castex described the killings as an "odious crime" and an act of "cowardice that is difficult to put into words".
- Military consequences -
No group has claimed responsibility for the attack but the region around Niamey has become a hideout for jihadist groups including the Islamic State in the Greater Sahara (ISGS), which has killed hundreds of troops and driven thousands of people from their homes.
Macron vowed there would be consequences, including military ones, from the attack.
The French military has a 5,100-member anti-jihadist force in the Sahel, which covers five countries, including Mali, Niger and Burkina Faso.
"We're pursuing action to eradicate the terrorist groups, with the strengthened support of our partners," Macron said.
A team of 11 specialist French investigators left for Niger on Tuesday, police and judiciary sources told AFP.
In Paris, French anti-terror prosecutors have launched an investigation into "murders with links to a terrorist enterprise" and "criminal terrorist association".
The NGO Acted, which has a network of 200 employees in Niger, said it would suspend its activities in the country.
Nonetheless, it would remain present in Niger, despite its horror at what it described as "senseless killings".
"There's no question of leaving the country or the region. We're there to help," Acted president Frederic de Saint-Sernin told French radio, RFI.
"The international community must recognise the contradiction in asking us to support people who live in such dramatic conditions, while at the same time leaving us alone to confront the violence of which we have become such easy targets," Acted co-founder Frederic Roussel told a news conference.