North Korea appears to be continuing efforts to develop a submarine-launched ballistic missile, a U.S. website monitoring the communist nation said Thursday.

The website 38 North said, citing recent satellite imagery of the North's Shinpo South Shipyard, that the North is believed to be forging ahead with development of the KN-11 SLBM, also known as Bukkeukseong-1, as well as a Gorae-class experimental ballistic missile submarine.

It said that about two months of unidentified work on the Gorae-class submarine appears to have been completed now. A removable tower used to support a rocket engine has also remained at the test stand for the past two months, allowing the North to more quickly conduct a pop-up test, it said.

"Despite legitimate concerns about North Korea's development of a SLBM and a ballistic missile submarine having a significant effect upon regional security, these developments represent an emerging rather than a current threat," 38 North said.

"Deployment of such operational systems will be an expensive, time-consuming endeavor for North Korea and there is no guarantee of success. Regardless, these programs require continual monitoring to ensure appropriate responses are in place if or when they reach fruition," it said. (Yonhap)