According to the government and local sources, an attack by the jihadist group Boko Haram on the Chadian army killed around 40 people overnight Sunday near the Nigerian border.

A vast expanse of water and swamps, Lake Chad’s countless islets serve as hideouts for jihadist groups, such as Boko Haram and its offshoot Islamic State in West Africa, who make regular attacks on the countries’ army and civilians. Boko Haram launched an insurgency in Nigeria in 2009, leaving more than 40,000 people dead and displacing two million, and the organisation has since spread to neighbouring countries.

In June, the International Office for Migration recorded more than 220,000 people displaced by attacks from armed groups in Lake Chad province. Chad is an important ally for French and US forces aiming to fight jihadists in the Sahel, which has become the epicentre of global terrorism under attack by factions loyal to al Qaeda and Islamic State.

Mali, Niger and Burkina Faso have ended military operations with the US and France in recent years and have turned to Russia for support instead.