S. Korea keeps close tabs on N. Korea's missile sites

South Korea has been maintaining high military alertness and close surveillance of North Korea to monitor signs of additional nuclear tests or provocations, the defense ministry said Monday.

Following Pyongyang's third atomic test in defiance of international warnings, Seoul has been closely monitoring the North, which has threatened to launch a long-range rocket if the U.N. Security Council issues tougher sanctions for the Feb. 12 nuclear test.

"The military considers there is still a threat of an additional nuclear test and possibility of a military provocation by the North," Army Col. Wi Yong-seop said in a briefing. "South Korea and the U.S. forces are intensively operating their intelligence assets to closely monitor the North Korean military's activities."

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