4 South Korean construction workers freed after being kidnapped in southern Nigeria

Four South Korean construction workers who were kidnapped in southern Nigeria have been freed.

The four employees of Hyundai Heavy Industries Co. were preparing for the construction of factories when they were abducted by unidentified gunmen Monday in Bayelsa state.

Seoul's Foreign Ministry said in a statement Saturday that the South Koreans were released Friday (local time) after "persistent persuasion." It did not disclose details of the negotiations.

The statement also provided no details about a Nigerian worker who was kidnapped along with the South Koreans. The ministry department handling the case did not answer calls. Hyundai said it had no information.

Kidnappings for ransom are frequent in Nigeria's oil-rich delta. Experts say kidnappers who once targeted mainly expatriate oil workers have recently shifted their focus to wealthy Nigerian families.