Islamic State said on Thursday that its West African branch had caused a helicopter collision in Mali in which 13 French soldiers were killed this week, but it did not provide any evidence for its claim, the SITE intelligence group reported.

The Islamic State in West Africa Province (ISWAP) said the helicopters collided after one of them retreated under fire from ISWAP fighters, according to a statement shared by U.S.-based SITE, which monitors jihadist websites.

The deaths of the soldiers late Monday represent France’s biggest military loss in three decades. The 13 troops were killed during a counterterrorism combat operation in Mali, when the two helicopters the troops were on slammed into each other.

Forty-one French soldiers have been killed in Mali since France launched its Barkhane counterinsurgency operation against Islamist militants in the Sahel in 2014.

The latest deaths draw attention to the roughly 4,500 French troops stationed across West Africa — raising questions about whether they are stretched too thin.

France is supporting a so-called G-5 Sahel alliance, grouping five area countries against armed extremist groups. But experts say the militant groups are strengthening. Regional forces and U.N. peacekeepers have come under attack. Some commentators say France does not have enough military support and the G-5 Sahel alliance has yet to achieve even a symbolic victory.

Source: Reuters