SEOUL -?The Republic of Korea's defense ministry said Thursday that the military is preparing for possible launch of ballistic missiles by the Democratic People's Republic of Korea (DPRK) at or around one of its most important national holidays.

Defense Ministry spokesman Moon Sang-Kyun told a press briefing that the military is closely monitoring and preparing for the DPRK's possible launch of ballistic missiles such as Musudan missiles.

Multiple ROK government sources were quoted by Yonhap news agency as saying that the DPRK had deployed one to two mobile Musudan missiles about 20 days ago to its eastern Wonsan area.

Those missiles, which are allegedly capable of striking parts of the US territory such as Guam and the outer reaches of Alaska, are highly likely to be launched on Friday that marks the so-called Day of the Sun, according to the sources.

The Day of the Sun is an annual public holiday in the DPRK that falls on April 15 to commemorate the birthday of Kim Il Sung, founder of the country and grandfather of current leader Kim Jong Un.

If launched, it would mark the first time that Pyongyang test-fires Musudan missiles and also the first time that the country launches ballistic missiles from a mobile launcher. Pyongyang is known to have deployed around 50 mobile Musudan missiles.

The ROK's military has reportedly dispatched an Aegis-equipped destroyer to the East Sea to detect and track the possible launch of Musudan missiles.

The DPRK has twice launched a three-stage rocket, which was condemned as a disguised test of ballistic missile technology, from a stationary launch pad.

The latest long-range rocket launch from a fixed site was carried out on Feb. 7, about a month after Pyongyang detonated what it claimed was its first hydrogen bomb on Jan. 6, the fourth of its nuclear test.

Unlike the launch from a stationary site that can be detected by spy satellites as it takes time to prepare, mobile launches are very hard, in case of military conflicts, to spot as the mobile launchers can move to another position before shooting missiles.

The ROK's military has also monitored possibility for the DPRK's fifth nuclear test since top DPRK leader Kim Jong-un gave orders on March 15 to test a nuclear warhead and ballistic rockets capable of carrying the warhead.

Pyongyang has claimed that it possessed a miniaturized nuclear warhead and mastered the technology of a re-entry vehicle, key to developing an intercontinental ballistic missile (ICBM).

Moon, Seoul's defense ministry spokesman, said that Pyongyang can conduct another nuclear test at any time when the leadership decides.

Regarding CNN's Wednesday report that the DPRK could launch either its KN-08 or KN-14 mobile ballistic missiles, the spokesman said that it would be possible.

The KN-08 is known as a long-range mobile ballistic missile that can strike the northwestern region of the US mainland. The KN-14 is alleged to be a more precise version of the KN-08.

The spokesman, however, noted that the DPRK has yet to issue a no-navigation zone in waters off the country, widely seen as a sign to launch ballistic missiles.

A ROK government official was quoted by Yonhap as saying that there is a possibility for the DPRK not to launch the mobile ballistic missiles, adding that stricter international sanctions would be taken if Pyongyang fires the Musudan missiles into the Pacific Ocean.