CAIRO, June 15 (Reuters) - The United Kingdom Maritime Trade Operations (UKMTO) said on Saturday that the crew of a merchant vessel had been evacuated and the ship was on fire and sinking, referring to an incident that took place 98 nautical miles southwest of Yemen's Aden on June 13. (Reporting by Enas Alashray and Hatem Maher; Editing by William Maclean)