(File photo)

SEOUL, June 21 -- The Democratic People's Republic of Korea (DPRK) has deployed what is believed to be its intermediate-range Musudan ballistic missile in its east coast, Yonhap news agency reported on Tuesday citing a government source.

The source, however, was quoted as saying that no immediate sign of firing has been detected yet.

An official at South Korea's defense ministry told Xinhua that the military is closely watching relevant situations.

The Musudan missile, known to be capable of hitting part of the U.S. territory such as Guam and the outer reaches of Alaska, was test-launched four times, one on May 31, two on April 28 and one on April 15 each.

However, the Seoul's military believed that all of the four test-firings failed as the missiles exploded in mid-air or crashed in waters several seconds after lift-off.

Pyongyang has allegedly deployed the Musudan missiles since 2007. The ballistic missile is considered especially threatening as it if fired from a mobile launcher, making it hard to detect and track in times of military conflicts. It can also carry a nuclear warhead.

The DPRK may test-launch the deployed Musudan missile around the 66th anniversary on June 25 of the three-year Korean War or June 29 when the DPRK's fourth session of the 13th Supreme People's Assembly (SPA) will be convened.

The first session of the 13th SPA re-elected top leader Kim Jong Un as the first chairman of the National Defense Commission (NDC) in April 2014. The SPA, the highest legislative body of the DPRK, is convened once or twice a year.

The possible fifth test-firing of the Musudan missile would be in line with Kim's order on March 15 to test a nuclear warhead and ballistic rockets capable of carrying the warhead"in a short time."

After the seventh ruling Workers'Party of Korea (WPK) congress that lasted four days through May 9, the DPRK repeatedly made dialogue overtures toward South Korea to talk about military matters in order to defuse tensions on the Korean Peninsula.

Seoul, however, had rejected the proposals as Pyongyang had yet to express its willingness to denuclearize. South Korea held fast to its position that no dialogue would be held with the DPRK unless Pyongyang shows its denuclearization will through sincere actions.