Gidami district, in a remote area of Oromia region that borders South Sudan, was under rebel control for two months.

It is feared those missing may be being held captive by the OLA.

"The abductees are government civil servants, and members of the local administration," said Tesema Wario, the head of security in that area.

The OLA has not said anything about their whereabouts.

The group is accused of targeting and killing dozens of officials in the restive Oromia region, which it always denies.