The aid agency GOAL says two of its Sudanese aid workers are "unaccounted for" after an incident in the Darfur region. A third worker for another agency is also missing.

The staff were abducted by an unknown group while driving on a "routine assignment" assignment while travelling by vehicle on a routine assignment close to Kutum town in North Darfur on Wednesday.

A fourth person - a driver also working for GOAL - was also abducted but was later released.

The chief operations officer for GOAL, Jonathan Edgar, says the crisis management team from the agency is working to determine the next course of action.

GOAL says it is in contact with the families of the staff members involved.