LONDON - Unknown assailants attacked a gas tanker off the coast of Yemen close to the Bab al-Mandab waterway in the latest flare up in an area through which much of the world's oil passes, shipping and security officials said on Wednesday.The incident, the first attack on a commercial ship since July, followed missile attacks in recent weeks on military craft, including US navy vessels, which were launched from Yemen that had already raised risks for merchant shipping.Shipping group Teekay said its LNG (liquefied natural gas) tanker Galicia Spirit "experienced a suspected piracy attack whilst off the coast of Yemen" on Oct. 25."No third parties managed to board the vessel during the incident and all crew members are safe and have been accounted for," Teekay said in a statement."As a precaution, the vessel had a Djibouti warship in attendance when heading away from the area. She has now left the high risk area without any further issues," it added without further details.Maritime security sources said the incident occurred near Perim Island, which is about 14 km from the southern Yemeni coast and the site of a lighthouse for ships passing through the Bab al-Mandab.British maritime security firm MAST said a small vessel had approached the tanker and fired a rocket propelled grenade (RPG). "MAST understands that the vessel had no armed security team on board, and that the vessel sustained small arms fire as well as the RPG," it said. "It is unclear whether this is a terrorist attack or piracy."