SEOUL, The Navy said Wednesday it has been staging annual maritime drills this week to boost readiness against North Korean naval threats and honor South Korean sailors killed near the western inter-Korean sea border. The five-day drills began Monday in waters off the country's eastern, western and southern coasts, after the nation commemorated the 55 service members, who died in action while defending the Northern Limit Line (NLL) from 2002-2010, on West Sea Defense Day on Friday. For the drills, the Navy said it mobilized some 20 warships, including the 3,200-ton ROKS Gwanggaeto the Great destroyer, as well as about 10 planes, such as P-3 maritime surveillance aircraft. The 2nd Fleet, headquartered in Pyeongtaek, 60 kilometers south of Seoul, will stage drills focusing on countering threats near the NLL, as well as live-fire exercises against enemy warships and submarines, according to the Navy. The 1st Fleet conducted live-fire anti-submarine drills in the East Sea, while the 3rd Fleet carried out dri lls in the South Sea with a focus on defending major ports. Waters near the NLL in the Yellow Sea have been a flashpoint between the two Koreas, where three bloody naval skirmishes took place in 1999, 2002 and 2009. In March 2010, Pyongyang torpedoed a South Korean warship near the boundary, killing 46 sailors on board. In November that year, the North bombarded the South's border island of Yeonpyeong, killing two civilians and two Marines. North Korea does not recognize the de facto sea border and claims a self-drawn boundary south of the NLL. Source: Yonhap News Agency