Lee: S. Korea needs to be on guard

South Korea needs to be alert to potential North Korean provocation following the death of Kim Jong Il, President Lee Myung-bak said Wednesday. Lee visited South Korean troops guarding the demilitarized zone, the border with North Korea, Yonhap News Agency reported. A spokesman, Park Jeong-ha, said Lee traveled to the 5th Infantry Division base in Yeoncheon, about 50 miles north of Seoul. \"North Korea is showing a very belligerent attitude,\" Lee said, adding that South Korea needs a \"watertight defense posture\" to prevent a \"provocation.\" Kim Jong Il died in December and was quickly succeeded by his third son, Kim Jong Un, who is believed to be still in his 20s and with limited experience. South Korean officials have expressed concern the new leader might involve his country in an act of war to bolster his credibility as a leader.