LAGOS (AFP) - Pirates have hijacked a Singapore-owned oil tanker in Nigerian waters, the third attack in just over two weeks in the Gulf of Guinea, the International Maritime Bureau said Wednesday.
The group said the tanker was seized within the port of Lagos, but Nigerian authorities insisted the attack happened farther offshore.
The vessel, which had 23 crew on board, was laden with fuel, IMB's Kuala Lumpur-based piracy reporting centre said, adding that the pirates were sailing the ship into the open sea.
It did not say how the pirates hijacked the tanker on Tuesday evening.
"We have informed the Nigerian authorities who are taking action," Noel Choong, head of the IMB's Malaysia-based piracy reporting centre told AFP.
The crew members had locked themselves in a safe room, said Choong, who added: "We are concerned about their safety and the spate of hijackings."
Nigeria's navy spokesman confirmed the attack, saying efforts were being made to track down the tanker.
"The vessel was hijacked last night off the coast of Nigeria. We are trying to get the details of the seizure but everything is being done to ensure the safety of the crew," Commodore Kabir Aliyu told AFP.
The Nigeria Ports Authority (NPA) denied reports that the vessel was hijacked within the Lagos port complex.
"There has been no hijacking of vessels in the Lagos ports. In fact, it cannot happen and it has never happened. If there was any seizure it would be on the high sea," NPA spokesman Michael Ajayi told AFP.
Pirates hijacked and looted two oil tankers off nearby Togo last month. The two ships and all crew members were later freed.
The IMB's Choong said the same criminal syndicate could be behind the latest attack since the modus operandi was the same.
"They would seize the ship for about five days -- ransack the crew's cabin and syphon the oil to another pirate vessel," he said.
The IMB has repeatedly warned ships plying the Gulf of Guinea off the west coast of Africa to be vigilant and called on authorities to step up patrols, saying last year the region was emerging as a new piracy "hot spot".
The area has seen 37 attacks, including several hijackings, kidnappings and killings, so far this year. Pirates usually target cargo, loading it onto other ships to sell on the black market.
Nigeria and nearby Benin launched joint patrols last year in a bid to combat the problem.