Korea-U.S. Combined Forces Command upgraded North Korea surveillance status by one notch to Watchcon 2 on Thursday, in expectation of more provocations following a nuclear test Monday. It was the first time since the North's first nuclear test in October 2006 that the CFC upgraded the Watchcon status to level 2.

There were no immediate signs of impending provocations, but South Korean military authorities are on alert since they believe North Korea will carry out provocations along the Northern Limit Line, the de facto maritime border in the West Sea, the Joint Security Area in the truce village of Panmunjom, or along the demilitarized zone.

In a press briefing Thursday, Defense Ministry spokesman Won Tae-jae said increased Watchcon status means boosting "aerial and other reconnaissance assets, intelligence-gathering assets, and analyzing personnel."

He said the intent is to keep close watch on North Korean army movements.

North Korea launched five short-range missiles into the East Sea on Monday and Tuesday, but did not fire any missiles into the West Sea although it had declared it off-limits area to ships from Monday until Wednesday. A South Korean military source said, "It seems the North did not fire any missiles into the West Sea for fear of accidents because many Chinese fishing boats are active there."

Meanwhile, UN Command on Thursday commented on North Korea declaring the armistice null and void after South Korea joined the U.S.-led Proliferation Security Initiative. "The armistice remains in force and is binding on all signatories, including North Korea," the UNC said. "The armistice has served as the legal basis for the cease-fire in Korea for over 55 years and significantly contributes to stability in the region."