Pirates have seized a Saudi-owned super tanker fully laden with oil off east Africa.
The hijacking, 830km southeast of Mombasa, Kenya, took place on Saturday in an area far beyond the Gulf of Aden, where most of the attacks on shipping have taken place.
Some foreign navies have begun patrols in the area as a result.
The Sirius Star had been heading for the US via the Cape of Good Hope at the southern tip of Africa, skirting the continent instead of heading through the Gulf of Aden and then the Suez Canal.
The vessel holds up to 2m barrels of oil - more than one quarter of Saudi Arabia's daily exports.
'This is unprecedented. It's the largest ship that we've seen pirated,' said Lieutenant Nathan Christensen, a spokesman for the US Fifth Fleet. 'It's three times the size of an aircraft carrier.'
Well over 60 vessels have been hijacked this year, driving up shipping insurance premiums and pushing some vessels to take longer routes between Asia and Europe than passing through the Suez Canal - potentially increasing the cost of traded goods.
