North Korean leader Kim Jong-un speaks with a senior military staff while inspecting a new tactical missile weapons system in an undisclosed site of the country in the photo released by the North's Korean Central News Agency on May 15. Yonhap

North Korea has made numerous changes at most of its ballistic missile bases over the last five years in an indication of its efforts to elevate the status of its Strategic Force, a unit tasked with operating long-range and other key missile systems, a U.S. monitor said Monday.

Citing satellite imagery taken in March, Beyond Parallel, a project of the Washington-based Center for Strategic and International Studies, released its analysis of the changes that focused on replacing outdated housing and improving food availability at those bases.

The bases are among about 15-20 known ballistic missile operating bases and ballistic missile support facilities that have never been declared by the North, it said.

"The timing and nature of these developments across multiple ballistic missile operating bases indicate that they are a component of (North Korean leader) Kim Jong-un's ongoing efforts to elevate the Strategic Force's status and improve its readiness," the monitor said in the analysis article.

"Many of the observed changes have focused on replacing outdated housing and improving food availability, indicating a concerted effort to continue improving the quality of life and morale of the Strategic Force troops and their families," it added.

Among the bases mentioned was the Hoejung-ni Missile Operating Base, located 338 kilometers north of the Demilitarized Zone (DMZ) separating the two Koreas. Along with several other northern missile bases, it forms the North's "rear ballistic missile belt," it said.

"The headquarters area has seen some minor changes, including the addition of landscaping, the razing of one building and the addition of several monuments," it said.

Beyond Parallel also looked into changes at the Kal-gol Missile Operating Base, 52 km north of the DMZ. The base, along with some other bases, forms North Korea's "forward ballistic missile belt," it said.

"Adding training launch pads indicates an effort to improve training and operational readiness," it said, touching on some of the changes that took place at the base.

The analysis came as Pyongyang has been doubling down on its ballistic missile programs, in what was seen as a move to bolster its nuclear delivery capabilities. (Yonhap)