Four United Nations peacekeepers were killed in an attack by jihadists on their camp in Aguelhok in northern Mali, the U.N. mission in Mali said Friday.

The U.N. mission said that helicopters were dispatched to the scene to evacuate the wounded from the camp, which houses mostly Chadian peacekeepers.

The U.N. mission said that the attackers suffered heavy losses and had abandoned several of their dead at the site of the attack.

Mali has been trying to contain an Islamic extremist insurgency since 2012.

Islamic extremist rebels were forced from power in Mali's northern cities with the help of a 2013 French-led military operation. However, the insurgents quickly regrouped in the desert and began launching frequent attacks on the Malian army and its allies fighting the insurgency.

The extremists have expanded their reach well into central Mali, where their presence has inflamed tensions between ethnic groups in the area.