Washington CNN  — 

North Korea may be close to launching a submarine capable of firing missiles and is making efforts to conceal its preparations, new commercial satellite images obtained by CNN appear to show.

The images from the Middlebury Institute and Planet Labs, appear to show North Korea making progress readying the vessel at the Sinpo South Naval Shipyard along the central coast of the country off the Sea of Japan.

North Korean leader Kim Jong Un visited the base in July to inspect progress on the submarine, which may already be operational, according to analysts.

“North Korea has erected a structure in the secure boat basin to hide the new submarine,” said Jeffrey Lewis, director of the East Asia Nonproliferation Program at the Middlebury Institute. “This suggests that the submarine has been launched or will be soon.”

CNN has asked the Pentagon for comment.

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When Kim inspected the construction of the submarine in July, North Korea’s state-run Korean Central News Agency (KCNA) said Kim had been briefed about the vessel’s operational and tactical data and combat weapon systems, and said it would deployed to North Korean territorial waters “soon.”

The United States assessed that the photos of Kim’s visit released by KCNA in July likely showed a refurbished submarine that Washington had been aware of for more than a year, according to a senior US official with direct knowledge of the assessment.

The Kim regime has sought to build a viable nuclear-armed submarine to enhance its deterrence capabilities analysts say, as those vessels are harder to track and destroy as opposed to land-based missiles. North Korea successfully test-fired a submarine-launched ballistic missile in 2016.

Dave Schmerler, a senior research associate at the James Martin Center for Nonproliferation Studies, said the new images show a structure with netting on top that might be used to possibly conceal the submarine in the water as well as the presence of a truck crane, though he cautioned he could not say for certain while only using optical imagery.

“This work is in preparation for the launching of their new submarine but we can’t predict when that will happen yet,” Schmerler said.

Pyongyang is believed to have a fleet of about 70 submarines, but experts say most of them are likely old and currently unable to fire nuclear-armed ballistic missiles.

Randall Shriver, assistant secretary for Indo-Pacific Security Affairs, told CNN last month that ongoing activity revealed by commercial satellite imagery at the North Korean shipyard was concerning.

“We see very intentional modernization,” on the part of North Korea, Shriver said. “If you extrapolate far enough, they’re looking for the capability that makes them a more potent adversary.”

While North Korea has put a moratorium on testing long-range missiles following three meetings between President Trump and Kim, it has continued to test short-range ballistic missiles and has made no firm commitments to stop testing submarine launched missiles.