South Korea's President vowed relentless retaliation against North Korea if provoked again. North Korea shelled front-line Yeonpyeong Island near the tense western sea border last month, killing four South Koreans. On Monday, President Lee Myung-bak used his regular radio address to vow to get tougher with any new provocation by North Korea, according to a report of the Associated Press. «We have now been awakened to the realization that war can be prevented and peace assured only when such provocations are met with a strong response,» Lee said. «Fear of war is never helpful in preventing war.» He said South Korea's military «must respond relentlessly when they come under attack.» Lee urged South Koreans to be more united on national security.