North Korea threatened on Thursday to launch a "sacred" nuclear war against South Korea if it attacks, as Seoul staged military exercises that have raised already high tensions on the peninsula. Defence chief Kim Yong Chun said North Korea was fully prepared to launch a war and would use its nuclear capabilities if attacked and warned the South against intruding even the smallest amount on its territory. North Korea's anger has been piqued this week by South Korea's staging of live-fire drills on Yeonpyeong Island, which was shelled by the North's artillery on November 23.