North Korea warned on Sunday that it would 'mercilessly retaliate' if a firing drill at sea this week by the South Korean military violates the North's territorial waters, according to dpa. A similar drill triggered a North Korean artillery bombardment in November 2010 that killed four South Koreans on the island of Yeonpyeong. The two sides are at odds about where the sea border is. The warning, which accused the South of deliberate provocation, came in an statement carried by the North's official media. It charged that the drill would imperil the overall situation on the Korean peninsula. Yonhap, the South Korean news agency, said Seoul had informed Pyongyang the 'routine' exercise would take place Monday near five islands at the sea border. South Korean and US forces were also to begin Monday a joint, five-day anti-submarine exercise as a deterrent to the North. That exercise off the western coast was announced last week.
