Berlin -

Pirates boarded an offshore tugboat and kidnapped four crew members off the Nigerian coast, the International Maritime Bureau reported on Monday.

The attack took place on Sunday, off the coast of Bayelsa.

The bureau said that pirates, armed with guns, attacked and boarded the offshore supply vessel. The sailors were not injured and the boat reached a safe port.

There was no further information immediately available.

Last week, five crew members of a tanker were kidnapped off the oil-rich Niger delta, the vessels' operating company said.

Armed pirates boarded the tanker SP Brussels on December 17, some 64 kilometres off the Nigerian coast, and abducted five crew members after looting the vessel, Germany-based Medallion Marine said.

Those sailors who remained on board sailed on and, on Wednesday, arrived at the Nigerian port of Lagos.

Kidnapping and piracy have become a booming business for armed bandits in the West African country. Also last week, four South Koreans and two Nigerians working for Hyundai Heavy Industries Co were kidnapped at gunpoint in the Niger delta.

In mid-October, pirates kidnapped seven crew from a boat operated by French shipping company Bourbon SA, off the Nigerian coast.

While piracy has decreased off the Somali coast in the Gulf of Aden, “the Gulf of Guinea is becoming the new dangerous maritime area in Africa,” warned the London-based think tank International Crisis Group. - Sapa-dpa