Pirates hijacked a cargo ship delivering UN food aid to northeastern Somalia on Sunday, officials said. The ship, NV Rozen, had just delivered 900 metric tons of food aid in the semiautonomous region of Puntland in northeastern Somalia when the pirates struck, said Stephanie Savariaud, a spokeswoman for the UN's World Food Program. It was not immediately known if any of the 12 crew members aboard - six from Sri Lanka and six from Kenya - were injured in the attack. "We know it has been hijacked by pirates but we do not know how many pirates there are," Savariaud said. The ship was contracted by the WFP to deliver food aid to Somalia. "The pirates have not made any demands yet," said Andrew Mwangura, head of the Kenyan chapter of the Seafarers Assistance Program. The ship is currently being held close to the island of Ras Afun, just off the Puntland coast. The ship has lost contact with its home port of Mombasa in Kenya and it is unclear if the hijackers are armed, said Mwangura. Piracy is rampant off the coast of Somalia, which has no effective government of its own to respond. The Horn of African nation has been in chaos since warlords overthrew a dictator in 1991 and turned on each other. In 2005 the number of reported incidents was 35, compared with two in 2004, according to the International Maritime Bureau. The bandits target both passenger and cargo vessels for ransom or loot. Somalia's 3,000-kilometer coastline is Africa's longest.