In a dramatic escalation of high seas crime, Somali pirates hijacked a Saudi supertanker loaded with crude oil hundreds of kilometers off the coast of East Africa - defeating the security web of warships trying to protect vital shipping lanes. The takeover demonstrates the bandits' heightened ambitions and capabilities: Never before have they seized such a giant ship so far out to sea. Maritime experts warned that the broad daylight attack, reported by the US Navy on Monday, was an alarming sign of the difficulty of patrolling a vast stretch of ocean key to oil and other cargo traffic. The MV Sirius Star, a brand new tanker with a 25-member crew, was seized at about 10 a.m. Saturday more than 833 kilometers southeast of Mombasa, Kenya, the Navy said. The area lies far south of the zone where warships have increased their patrols this year in the Gulf of Aden, one of the busiest channels in the world, leading to and from the Suez Canal, and the scene of most past attacks.