Three more South Korean vessels entered the volatile waters of the Persian Gulf on Monday, bringing to nine the total number of local vessels currently operating in the region. The Ministry of Maritime Affairs and Fisheries said that it would be difficult for Korean shipping companies to change their planned operations - which are subject to contract obligations - unless increasingly serious terror risks arise in the region. An al-Qaida-linked terrorist group reportedly threatened last Friday to attack maritime vessels shipping goods to U.S. forces in Iraq. According to South Korean media, the terrorist group named nine shipping companies as potential targets on an Islamic Internet site, including one South Korean firm.