Recent satellite imagery shows North Korea is forging ahead with development of a submarine-launched ballistic missile, the website 38 North said Tuesday.

The imagery taken of the North's Shinpo Shipyard on April 29, six days after the North's latest SLBM test, shows that a submersible missile test stand barge has been moved from its normal position.

"This shift in location suggests that the SLBM program may be moving towards a more advanced stage of development where the need for a submersible test stand barge has diminished," 38 North said.

"That conclusion appears to be reinforced by recent test launches from the submarine itself rather than the barge."

It described the North's SLBM test as "successful."

"While North Korea's submarine-launched ballistic missile program is making progress, these activities appear in line with previous estimates that the first ballistic missile submarine and operational missiles are unlikely to become operational before 2020," it said. (Yonhap)