A security unit on board the British-flagged, Norwegian-crewed Stolt Apel fired at six gunmen aboard two speed boats that had fired an RPG7 rocket-propelled grenade at the 23,000t chemical tanker and were attempting to board the ship. The incident, on 17 May, unfolded 120km off Mukulla in the Gulf of Aden, the UK Maritime Trade Organisation reported.Maritime security company Dryad Global said this was the ninth such incident this year in the international transit corridor through the Gulf of Aden.