"North Korea has been detected to have deployed a Musudan missile(s) in the vicinity of Wonsan's Hodo Peninsula," one source told Yonhap News Agency.

"After deploying them some 20 days ago, the North has not withdrawn them," the source said. "Given the fact, North Korea is likely to venture a launch on the occasion of Kim Il-sung's birthday."

Defense ministry spokesman Moon Sang-gyun also confirmed the possibility of an imminent ballistic missile launch by Pyongyang.

"On March 15, (North Korean leader) Kim Jong-un ordered a nuclear warhead detonation test and test-launches of ballistic rockets that could carry nuclear warheads," Moon said in a press briefing, referring to its recent series of military rhetoric against the South.

"In line with that, our military is closely following the possibility of North Korea's fifth nuclear test or launches of ballistic missiles like the Musudan," he said.

Further asked to confirm CNN's recent report on North Korea's preparations to launch a ballistic missile, Moon said, "There is a possibility and we are stepping up our surveillance."

On Friday, North Korea marks the 104th birthday of the late North Korean founder and leader Kim Il-sung.

The North has celebrated the "Day of the Sun" with elaborate military events in the past, with experts predicting that the event for this year will be marked with a ballistic missile launch. 

Other military sources said the missile or the missiles were loaded onto a transporter-erector-launcher or TEL, a mobile missile launcher.

If the launch takes place, it will be North Korea's first test-launch of the intermediate-range ballistic missile also known as BM-25.

North Korea is banned from launching ballistic missiles under a series of United Nations Security Council resolutions.

With a range of up to 4,000 kilometers, the missile could fly over South Korea and Japan to reach as far as Guam, where United States military forces are stationed.

North Korea is believed to be keeping an arsenal of about 50 Musudan missiles.

Sources said North Korea may inform the International Maritime Organization, a global shipping regulation body, of its launch plan before pushing ahead, but the country doesn't seems to have taken such a step yet.

One government official said if North Korea goes ahead with a launch and "the fired missile passes over Japan and drops in the Pacific Ocean, it will lead to ever more powerful sanctions against North Korea."

As for a possible nuclear test, Moon said, "North Korea is (technically) ready to conduct a nuclear test at any time."

Any further provocation by North Korea is sure to escalate inter-Korean tension which is already running high after North Korea's nuclear test in January and a long-range rocket launch in February. (Yonhap)