Niger Delta militants have seized a vessel belonging to the US oil giant, Chevron, a spokesman of special troops deployed to provide security in the region said Wednesday.

The vessel was carrying a Portuguese citizen, a Ukrainian and nine Nigerians when it was seized, Lieutenant Colonel Sagir Musa said adding that no group has claimed responsibility for the seizure.
The vessel was seized while sailing from Onne port in Port Harcourt, Rivers State, to Escravos in Delta State, Sagir said.
He said the vessel might be carrying supplies and other essential materials for the Escravos oil production Platform.
Though the exact location of its seizure was not known, it was suspected to have been taken at Krakrama area near Fouche Island, some 30 nautical miles from Port Harcourt, the official said.
'The militants are demanding a ransom of 250,000 dollars for the release of the vessel and the occupants,' he added.
Kidnapping and destruction of oil production facilities in the Niger Delta has contributed to the sky-rocketing of prices of crude oil in the international market.
Militants in the region claim they engage in kidnapping and vandalism to drive home a demand made on the Nigerian government to allow people of the impoverished Niger Delta region have a greater say in the affairs of its oil and gas deposits.