Pirates on Thursday released five Pakistani crew kidnapped from an oil tanker off the Nigerian coast two weeks ago, security sources said.
Increasing piracy in the Gulf of Guinea region is jacking up costs for shipping firms operating there.
Armed pirates had attacked the Nigerian-flagged MT Matrix and abducted five Pakistani crew members on May 25 about 40 nautical miles off the coast of the oil-producing Bayelsa state, a stretch of water frequently plagued by armed gangs.
Two security sources said the men, who worked for an oil servicing company, were released unharmed. There were two attacks in the Gulf of Guinea in April in which foreigners were kidnapped and released a few weeks later.
Security sources believe ransoms were paid – an increasingly lucrative business for criminal gangs who used to take more interest in simply stealing the oil on board the tankers.