Sunken Russian Ship Allegedly Carried Nuclear Submarine Reactors Destined For North Korea

The maritime industry publication The Maritime Executive, citing a new report from the Spanish outlet La Verdad, reported that the Russian cargo ship that sank last year off Spain’s southeastern Mediterranean coast was transporting undeclared components for two VM-4SG nuclear submarine reactors, allegedly with a port call planned in North Korea.

In December 2024, the Russian cargo ship Ursa Major sank under highly suspicious circumstances in waters between Spain and Algeria following reported engine room explosions. The ship’s owners characterized the incident as “an act of terrorism.”

Spanish authorities determined that blue-tarped objects on Ursa Major’s stern were likely unfueled naval nuclear reactor casings, each weighing roughly 65 tons. Investigators identified them as components of VM-4SG reactors, Soviet-designed naval nuclear reactors developed to power Russia’s nuclear ballistic-missile submarine fleet during the late Cold War and still in limited service today.

Here’s the report:

The circumstances of the vessel’s sudden sinking were suspicious, prompting the maritime captaincy to begin questioning the crew. Ursa Major’s master, Capt. Igor Vladimirovich Anisimov, initially told investigators the cargo consisted of more than 100 empty containers, two giant crawler cranes on deck, and two large components for a Russian icebreaker project, referring to the tarped objects near the stern. All cargo was reportedly bound for Vladivostok.

The two so-called “icebreaker components” were shipped as deck cargo and were visible to spotting aircraft during the ship’s earlier transit. Based on aerial surveillance, each object measured approximately 20 to 25 feet square, including crating, dunnage, and tarping.

Spanish authorities estimated their weight at roughly 65 tonnes each, indicating unusually high density. La Verdad reported that after the captain was pressed on the matter, he asked for time to think before telling investigators the items were merely “manhole covers.”

Documents reviewed by La Verdad show Spanish investigators ultimately identified the cargo as casings for nuclear submarine reactors, specifically two Soviet-era VM-4SG reactors.

As for the destination, Spanish authorities speculated the reactor components may have been intended for North Korea’s nuclear submarine program, which recently unveiled its first ballistic-missile submarine. Multiple analysts have suggested the new North Korean vessel likely benefited from Russian technical assistance for reactor design and could potentially incorporate a fully built Russian reactor. Russia is believed to owe North Korea a strategic debt following Pyongyang’s large-scale transfers of artillery shells and munitions that helped Russian forces stabilize and regain ground in eastern Ukraine.

The cause of Ursa Major’s sinking appears to have been kinetic. The shipowner told media there were three explosions and a 20-inch hole in the shell plating, while the captain confirmed the hole’s ragged edges were bent inward. This damage profile is consistent with an external explosion impacting the hull.

This report surfaced days after North Korea released new images of what it claims is its first nuclear-powered submarine, a platform framed as a direct challenge to American naval dominance in the region.

If the report that Ursa Major’s sinking was kinetic is accurate, the unresolved question is who executed the strike and under what operational authority.