North Korea is pouring “serious resources” into modernizing its naval forces, an effort that could eventually increase the threat to U.S. and South Korean vessels in the region, a U.S. think tank says.

Commercial satellite images show the North Koreans have been working aggressively since 2014 to upgrade training facilities, weapons systems, and special operations capabilities at the Munchon naval base on the country’s east coast, the U.S.-Korea Institute’s 38 North blog said Thursday.

It is part of leader Kim Jong Un’s strategy to improve North Korea’s conventional military capabilities and special operations forces in parallel with its nuclear and ballistic missile programs, experts said on a conference call to discuss the report.

“It appears that North Korea, at this point in time, is concentrating all of its naval sniper brigades on the east coast,” said Joseph Bermudez, who wrote the analysis for the U.S.-Korea Institute at Johns Hopkins University’s School of Advanced International Studies.