Benghazi, Libya — A Libyan river authority said an unidentified armed group has kidnapped three Filipino nationals and one South Korean working on a project south of the capital, Tripoli.

The authority managing the Great Man-Made River project said in a statement Friday the four foreigners, who work as engineers and technicians at a water project, were abducted and taken to an unknown destination. It said three Libyan workers were also abducted but were later released.

On Saturday, the authority said armed groups attacked another project area in southeastern Libya killing two Libyan workers there and kidnapping two others.

Abduction has emerged as a lucrative trade amid the breakdown of authority in Libya after it plunged into chaos following the 2011 uprising that toppled and later killed a longtime ruler.