The peacekeeping mission MINUSMA reported that when their patrol was ambushed in northern Mali on Friday, at least one United Nations peacekeeper was killed and four others suffered significant injuries.

The event happened close to the town of Ber in the Tombouctou region, which has seen a rise in jihadist activity during the previous ten years.

MINUSMA said on Twitter the patrol first encountered an improvised explosive device and was then hit with a direct fire attack.

It did not name perpetrators but said it was a “complex attack” and that updates on casualties would follow.

Islamist militants, some with links to al Qaeda and Islamic State, have been waging an insurgency in northern Mali since they hijacked a Tuareg rebellion in 2012.

The violence has spread across the Sahel region under the Sahara and beyond despite international military interventions to help local troops fight back.

Thousands have been killed and over six million displaced by the fighting, according to the U.N.

MINUSMA – the United Nations Multidimensional Integrated Stabilization Mission in Mali – currently has about 12,000 military personnel deployed in the country.

At least 303 MINUSMA personnel have been killed in hostile acts in Mali since the start of the mission in 2013, making it the deadliest U.N. peacekeeping mission in the world.