Attackers on motorbikes ambushed the group of aid workers as they drove through the giraffe reserve France has 5,100 troops deployed in the arid region south of the Sahara desert NIAMEY: French and Nigerien soldiers searched through a giraffe reserve and the surrounding area in Niger on Monday for traces of the gunmen who killed six French aid workers, a French military source said. France’s anti-terrorism prosecutor also opened an investigation into the incident, in which attackers on motorbikes ambushed the group as it drove through the reserve located 65 km (40 miles) from the capital Niamey — an area considered safe by the Niger government. The French aid workers were employed by the charity ACTED. A local driver working for the relief group and a guide were also killed. ACTED called the murders “senseless and cowardly.” “This heinous crime must not go unpunished, nor will it distract us from our commitment to support the people of Niger,” said ACTED, which has worked to help vulnerable populations in the country since 2010. No one has claimed responsibility for the assault. But France and other countries have warned people against traveling to parts of Niger where militants including Boko Haram and an affiliate of Daesh operate. “Military operations are ongoing today,” the military source said. In the clearest sign yet that France believes a militant group was behind the attack, the office of France’s anti-terrorism prosecutor said it was launching an investigation on suspicion of the involvement of a terrorist group. French President Emmanuel Macron said he shared their families’ grief. “Our determination to combat armed terrorist groups is resolute. The fight continues,” Macron tweeted. The reserve southeast of Niamey is home to West Africa’s last sizeable population of giraffe in the wild. In the wet season, thick green acacia bushes dot the flat, sandy plains. It is a popular attraction in Niger, a vast country that borders seven states in an unstable region including Libya, Mali, Chad, Algeria and Nigeria. France, a former colonial power in the region, has 5,100 troops deployed in the arid region south of the Sahara desert since 2013. The United States also has soldiers based in Niger. Nonetheless, militant violence has been on the rise.