About 53 soldiers and one civilian have been killed in an attack on an army post in northern Mali on Friday the government said, in one of the deadliest strikes against the West African country’s military in recent memory.

Government spokesman Yaya Sangare said on Saturday that the death toll remained provisional as corpses were undergoing identification and that the army was undertaking a combing operation on the ground with support from international forces, including French troops from the Barkhane operation and UN peacekeepers.

The attack follows jihadist raids in late September that underscored the increasing reach and sophistication of armed groups operating in the region.

From their stronghold in Mali, groups with al Qaeda and Islamic State links have been able to fan out across the Sahel, destabilizing parts of Niger and Burkina Faso.

Thirty-eight Malian soldiers were killed on September 30 in coordinated attacks on two army bases in central Mali, which has slipped from government control despite the presence of the French army and other international forces.