A Russian cargo ship, the Ursa Major, sank in the Mediterranean Sea between Spain and Algeria in December 2024 following explosions in its engine room. Spanish investigators now believe the vessel was deliberately sunk to prevent Russia from delivering advanced nuclear technology to North Korea.
The ship's captain later told investigators that items declared as "non-dangerous merchandise" were actually components for two nuclear reactors similar to those used in submarines. He believed the ship would eventually be diverted to the North Korean port of Rason.
The vessel was operated by Oboronlogistika, a company owned by the Russian Ministry of Defense. It had been under US and UK sanctions since Russia's invasion of Ukraine in 2022.
The sinking occurred two months after North Korea sent 10,000 troops to support Russia's war effort. Investigators believe this prompted Moscow to transfer nuclear technology to Pyongyang in return.
One week after the incident, the Russian spy vessel Yantar spent five days over the wreckage. US nuclear "sniffer" aircraft have also flown over the site twice in the past year.
South Korean intelligence reported in September 2025 that Moscow had already handed Pyongyang one nuclear reactor.