North Korea has displayed its cyberattack capabilities and advances toward making nuclear warheads, the country’s adversaries say. Now, the North appears to have shown progress in fitting submarines with missile launchers.

A report posted Thursday on the website of 38north, a prominent research group that focuses on North Korea, said commercial satellite imagery of a North Korean submarine, taken less than a month ago, indicates the vessel may have one or two vertical launching tubes for either ballistic or cruise missiles.

The submarine, first seen in July, could be a test bed for underwater missile launching, which would be harder to detect than land-based launchers, the report said. It was written by Joseph S. Bermudez Jr., an arms expert and authority on North Korea’s defense capabilities.

Mr. Bermudez cautioned, as have other Western defense experts, that North Korea is not believed to have the ability to launch missiles from submarines.