The United Nations refugee agency says it is "extremely concerned" about growing insecurity in eastern Chad.

The agency's comment comes a day after an armed group entered the Goz Amer refugee camp during a food distribution. The agency says the incident frightened the refugees, but there are no reports of casualties.

UNHCR says 118 staffers from various aid groups were unable to leave the camp Monday night. But it says the situation in the camp is calm Tuesday and that humanitarian workers can now leave.

The refugee agency says it is monitoring the situation closely. The agency runs 12 camps in eastern Chad that provide aid to more than 200,000 refugees from war-torn Darfur in Sudan.

Goz Amer sits about 100 kilometers from the Sudanese border.

The refugees fled fighting in Darfur that involves rebels, government forces and Khartoum-backed militias. Three years of fighting in Darfur has killed about 180,000 people and displaced 2 million others .

Some information for this report was provided by AP and Reuters.