The medical charity, Medicines Sans Frontiers, has suspended its operations in Amadi State after its base was looted in Mundri County over the weekend.
In a statement, MSF says the organization had completed carrying out an assessment in the area last Saturday, when their compound was raided by the gunmen.
Due to the incident, MSF says it evacuated all the staff there.
It appealed to all parties to respect the work of humanitarian aid workers.
Meanwhile, Amadi state information minister Victor Mabruk has confirmed the incident to Eye Radio.
“According to the information I got from the commissioner of Mundri, these boys took away mattresses, computers, telephones and other important documents,” Mr Mabruk told Eye Radio.
“We are trying our level best as a government to prevent this from happening again.”