* Would be most southerly west Africa pirate attack
* Angola is major oil exporter to China
* W.African piracy pushing up insurance, shipping costs
ATHENS/ABUJA, Jan 22 (Reuters) - A fuel tanker is suspected to have been hijacked by pirates off the coast of Angola, the ship's owners said on Wednesday, in what would be the most southerly attack to date by pirates off West Africa.
Pirate attacks jumped by a third last year off the coast of West Africa but were mostly confined to the Gulf of Guinea, around Africa's biggest oil producer Nigeria, where most of the hijacking gangs are believed to originate.
The 75,000 deadweight tonne Liberian-flagged fuel tanker MT Kerala lost contact with its Greece-based owner Dynacom on Jan. 18. The ship was last seen around seven nautical miles from the Angolan capital Luanda, according to a security source.
"It is suspected that pirates have taken control of the vessel," Dynacom said in a statement, adding it had no confirmation.
If true, it would be hundreds of miles (kms) further down the coast than the previously most southerly reported attack, when pirates hijacked a tanker off Gabon last year. They were suspected of siphoning oil from the vessel.
One security source said the MT Kerala was loaded with gasoil. Tankers seized by Nigerian gangs are often released after the oil, gasoline or other fuel on board is transferred to smaller vessels. Sometimes crew are kidnapped for ransom.
International navies are not actively engaged in counter-piracy missions in the region, unlike in the waters off Somalia, the piracy hotspot on the other side of the continent.
Angola is Africa's second biggest crude oil exporter after Nigeria, where pirate attacks have pushed up insurance costs for shipping firms and foreign oil companies. Angola is a major exporter to China.
"If substantiated, this latest incident demonstrates a significant extension of the reach of criminal groups and represents a threat to shipping in areas that were thought to be safe," said Ian Millen, director of intelligence at Dryad Maritime.
Millen said a suspicious tug boat entered northern Angolan waters last week and was tracked moving north from Angola towards Nigeria after the suspected attack, which could point to an extension of the reach of Nigerian gangs.
The Gulf of Guinea region is a major source of oil, cocoa and, increasingly, metals for world markets. (Reporting by Renee Maltezou in Athens and Joe Brock in Abuja; additional reporting by Jonathan Saul in London and Pascal Fletcher in Johannesburg; Editing by Alister Doyle)