WARRI: Police say gunmen have kidnapped 15 oil workers near Nigeria's petroleum capital of Port Harcourt in the latest apparent hostage-for-ransom incident.

A police spokesman, Deputy Superintendent Nnamdi Omoni, said Saturday that all the abducted are Nigerians working for the local oil industry service company Nestoil.

He says their bus was hijacked Friday about 100 kilometers (60 miles) southeast of their office in Port Harcourt.

Kidnappings of Nigerians and foreigners are common all over the country. In the oil-rich southern Niger Delta, they are carried out by ordinary criminals as well as militants demanding a greater share of oil riches for locals.

Hostages are usually released unharmed after ransom payments.

Last month, 14 passengers seized from a commuter bus near Port Harcourt were released after two days. It was not clear if ransoms were paid.