Somali pirates have hijacked a Yemeni ship loaded with steel, officials said on Tuesday, and one of Asia's biggest shippers said it was diverting vulnerable vessels away from the dangerous Gulf of Aden. Scores of attacks this year have brought the pirates millions of dollars in ransoms, hiked up shipping insurance costs, sent foreign navies rushing to the area, and left about a dozen boats with more than 200 hostages still in pirate hands. Among them is a Saudi supertanker seized on November 15 in the biggest ever hijacking at sea. Local sources said the gang holding it were demanding a $15 million ransom. Yemen's official SABA news agency said the Yemeni ship MV Adina was traveling from Mukalla port to the southern island of Socotra and had been due to dock on November 20 with 507 tons of steel. Yemeni security sources said the authorities were in touch with the pirates, who were demanding a $2 million ransom. The sources said the vessel was owned by Yemeni shipping firm Abu Talal and was carrying seven crew -- three Somalis, two Yemenis and two Panamanians.