Humanitarian work has been suspended until the weekend in a remote town in northeast Nigeria after a Boko Haram attack killed three aid workers, the U.N. said on Saturday.

The attack happened on Thursday evening in Rann, near the border with Cameroon, where nearly 80,000 people depend on emergency food aid and medical care.

At least one other aid worker was critically injured and another three were missing. Eight Nigerian soldiers were also killed. The aid workers are not believed to have been specifically targeted but were caught up in an attack on the military. Those killed were Nigerians working for the International Organization for Migration and the U.N. children's fund UNICEF. The injured and missing are also locals. Doctors Without Borders (MSF), which has worked in Rann since January 2017, announced on Friday it had suspended medical activities and withdrawn 22 staff. It said it would return "as soon as the conditions allow." At least 20,000 people have been killed and more than two million others made homeless in Boko Haram's insurgency since 2009. The conflict has also caused a humanitarian crisis in northeast Nigeria and the wider Lake Chad region, particularly chronic food shortages.