French Tiger helicopters on Oct. 21 struck a militant vehicle just across the Niger-Mali border, not far from the scene of an ambush in early October that killed four U.S. soldiers.

According to a Facebook post by the French Ministry of Defense, French Tiger helicopters pursued armed militants after the group fled across the Nigerien border into Mali.

The strikes against the militant group followed an attack that day against a Nigerien base near the town of Ayorou. Militants stormed the Nigerien outpost on motorcycles and pick-up trucks, killing at least 12 Nigerien police officers, according to the BBC.

The Nigerien outpost struck by the militants is not far from where four U.S. soldiers were killed in an Oct. 4 ambush.

Following the attack, Nigerien SA-342 Gazelle helicopters chased the militants across the border, where they were struck by French Tiger helicopters. The operation was coordinated between Nigerien and French forces, according to the French statement.

No group has claimed responsibility for the attack on the Nigerien outpost, but Alakhbar, a news outlet in Mauritania, reports that the Islamic State in the Greater Sahara, or ISGS, was behind the attack.

U.S. officials believe ISIS fighters also were behind the Oct. 4 ambush that killed four U.S. soldiers.

The French have roughly 4,000 soldiers operating in West Africa as part of Operation Barkhane.