GENEVA (AP) — U.N. agencies said Friday that tens of thousands of Nigerians are fleeing deadly attacks by armed groups and the continuing clashes between the rebels and national forces in the country’s troubled northeastern Borno state.

The latest rebel attack on Wednesday drove out as many as 80% of the population of Damasak, according to the U.N. refugee agency, who said up to 65,000 people were on the move.

“Assailants looted and burned down private homes, warehouses of humanitarian agencies, a police station, a clinic, and also a UNHCR facility,” the U.N. agency’s spokesman Babar Baloch told reporters in Geneva. It marked the third such attack in a week, he said.

There are “very worrying” reports of clashes between insurgent groups and Nigeria’s armed forces, spokesman Jens Laerke of the U.N. Office for the Coordination of Humanitarian Affairs, OCHA, said.

Armed groups have been attacking humanitarian facilities and at times conducting house-to-house searches, reportedly looking for civilian aid workers, he said.

Most humanitarian aid operations have been suspended in the area since Sunday because of the insecurity, Laerke said.

“The situation on the ground is extremely critical,” he said. “If this continues, it will be impossible — maybe for longer periods of time — for us to deliver aid to people who desperately need it.”

The incidents mark the latest violence in the Lake Chad basin area which in recent years has uprooted some 3.3 million people, the refugee agency said.