( CNN ) -- The hijacking of a container ship in the Indian Ocean Friday afternoon is evidence of a `` constantly expanding area of pirate activity '' off the Africa coast , military officials said . At least five pirates , using two small boats and a rocket-propelled grenade , boarded the MV Panama , a Liberian-flagged vessel operated by a U.S. company , according to a statement by the European Union Naval Force Somalia . The attack happened about 80 nautical miles east of the Tanzanian-Mozambique border , the statement said . `` This extreme southerly attack in the Somali Basin is a further example of the constantly expanding area of pirate activity , '' it said . Pirate attacks have become a frequent hazard for sailors off Somalia , which has had no effective central government since 1991 . The merchant vessel was sailing from Dar es Salaam , Tanzania , to Beira , Mozambique , when the pirates attacked , it said . There was not immediate word of the condition of the 23 crew members , who are all from Myanmar , it said . The European Union Naval Force Somalia is a multinational task force with the mission to escort merchant vessels carrying humanitarian aid of the World Food Program and vessels of the African Union Mission in Somalia . The mission is `` to protect vulnerable ships in the Gulf of Aden and Indian Ocean and to deter and disrupt piracy , '' it said . Despite a crackdown by an international naval flotilla in the region , pirates managed to seize 35 ships in the region between January and September , according to the International Maritime Bureau , which monitors attacks .
35 pirates board the MV Tanzania between January and September off Panama . Naval officials called it an `` extreme southerly attack '' Fate of the 23 crew members is unknown .