Four expatriates and two Nigerians working for the South Korean construction firm Hyundai Heavy Industries Limited were kidnapped Monday in southern Nigeria, police said.
A fisherman, Tare Kolugha, said he witnessed the abductions as the workers were travelling to their workplace in southern Bayelsa state.
Gangs have frequently abducted expatriates working in the oil-producing Niger Delta in ransom kidnappings, but Nigerians from wealthy families have increasingly become their targets in recent years.
Hyundai Heavy in Seoul confirmed the kidnappings, but said one of the Nigerians had apparently been released.
A 2009 amnesty deal in the Niger Delta led to a sharp drop in unrest in the region, but criminality remains widespread.
Late last month, two foreigners who were identified by the local media as Lebanese were kidnapped at a work site in the region.
And the 83-year-old mother of the Nigerian finance minister, Ngozi Okonjo-Iweala, was kidnapped from her home in Delta state and held captive for five days before being freed on Friday.