The five employees of Hyundai Heavy Industries Co. were preparing for the construction of factories when they were abducted by unidentified gunmen Monday in Bayelsa state.
Bayelsa State police chief Kingsley Omire said Saturday that the kidnappers "freely released" their hostages at about 9.30 p.m. Friday. He said no ransom was paid.
Seoul's Foreign Ministry said in a statement Saturday that the release was the result of "persistent persuasion."
Omire said no one was hurt and that the Bayelsa State government had a strict no-ransom police.
Kidnappings for ransom are frequent in Nigeria's oil-rich delta.
(Copyright 2012 by The Associated Press. All Rights Reserved.)