KINSHASA, Dec 8 (Reuters) - Three United Nations staff members were injured when their vehicle came under fire in eastern Democratic Republic of Congo on Wednesday, their agency said. Unidentified gunmen attacked a vehicle of the U.N. refugee agency UNHCR in North Kivu province"s Lubero territory. The staff"s military escort, provided by U.N. peacekeepers, then accompanied them to safety, a UNHCR spokesperson said. "Humanitarian actors working in displacement situations should not be a target," the spokesperson, Johannes van Gemund, said. Eastern Congo is home to a host of armed groups fighting over land and resources, and Congo"s underfunded army has struggled to contain the various threats, leaving civilians vulnerable to attack. Lubero has seen fighting in recent years between ethnic militias, primarily from the Hutu and Nande groups.