S.Korea holds firing drill despite N.Korea threat

South Korean troops have begun a live-fire artillery exercise near the disputed Yellow Sea border with North Korea despite the North\'s threats of retaliation, according to officials. Military officials said the \"routine\" drill, their second this year, would involve self-propelled howitzers, Vulcan cannon, mortars and Cobra attack helicopters. The defence ministry said the exercise began at about 10 am (0100 GMT) on Monday and would last one to two hours. Military officials notified North Korea of the scheduled drill through representatives at the truce village of Panmunjom on Sunday. Hours afterwards, the North\'s military vowed \"merciless retaliatory strikes\" if any shells land in waters claimed by Pyongyang. It said Seoul \"should not forget the lesson\" of the bombardment of Yeonpyeong island in November 2010, which killed four South Koreans. The North said that attack was in retaliation for a live-fire exercise which dropped shells into waters which Pyongyang considers part of its maritime territory. The 2010 attack briefly sparked fears of war and triggered a major South Korean military build-up on the islands. Seoul has vowed to hit back harder, using air power, for any fresh strike. Early Monday, Pyongyang repeated threats of possible retaliation. \"If the puppet warmongers preempt reckless firing despite our warning, they will not escape punishment thousands-fold severer than the past Yeonpyeong Island shelling,\" said a statement issued in the name of an official body called the Committee for the Peaceful Reunification of Korea. Pyongyang has taken a hostile tone towards Seoul since Kim Jong-Un, the youngest son of the late leader Kim Jong-Il, took over following the death of his father in December. South Korea says the drill is a regular monthly exercise designed to maintain combat-readiness in the flashpoint border region. Officials said residents of the frontline islands would be advised to relocate to safe zones before the firing begins.