The December 2024 sinking of the Russian cargo vessel Ursa Major has resurfaced after new reporting cited a Spanish parliamentary document referring to possible nuclear reactor components on board. The claims remain unproven, but the incident has renewed scrutiny of Russia’s military logistics, its relationship with North Korea, and the possibility that sensitive cargo was being concealed under a declared commercial manifest.

The sinking of the Russian cargo ship Ursa Major in the Mediterranean is again under scrutiny, almost a year and a half after the vessel went down between Spain and Algeria. The case has resurfaced now because of new reporting based on a Spanish parliamentary document dated 23 February 2026, which reportedly records that the ship’s captain told Spanish authorities the vessel was carrying components for two nuclear reactors similar to those used in submarines. That claim has not been independently proven, but it was not part of the original Russian public account of the incident.

The Ursa Major, formerly known as Sparta III, was a heavy-lift cargo vessel owned by Oboronlogistika, a company linked to Russia’s Ministry of Defence and subject to Western sanctions. The ship left Russia in December 2024 on what was officially described as a voyage from St Petersburg to Vladivostok. According to the company’s own statement on the sinking, the declared cargo included two port cranes, two large hatch covers for nuclear icebreaker reactors, a container of spare parts and 129 empty containers.

That declared cargo is one of the reasons the case continues to attract attention. Heavy cranes and reactor hatch covers would explain the need for a large transport vessel. The presence of more than 100 empty containers is less clear. Open-source analysts and journalists have since suggested that the containers may have concealed other material, possibly connected to nuclear reactor technology. This remains an allegation, not a verified fact.

The confirmed chronology begins on 23 December 2024, when the Ursa Major sank in the western Mediterranean after explosions on board. Fourteen crew members were rescued by Spanish maritime authorities and taken to Cartagena. Two crew members died. Early accounts said the vessel suffered an explosion in or near the engine room. The ship’s owner later said there had been three explosions on the starboard side near the stern, and described the incident as a “terrorist attack”.

Oboronlogistika also said that a hole of around 50cm by 50cm was found in the hull, with the edges bent inwards. This detail has been central to speculation that the vessel may have been struck from outside, either by an attached explosive device, a mine, or some form of underwater munition. There is no public proof for any of these theories. No state has acknowledged involvement, and no conclusive international investigation has established the cause of the explosions.

The more serious allegation is that the ship may have been carrying nuclear reactor components intended not for Vladivostok, but for North Korea. The Associated Press reported that a Spanish parliamentary document, citing the captain’s account to port authorities, referred to components for nuclear reactors similar to those used in submarines. The report does not prove that the cargo was destined for Pyongyang. Nor does it establish whether any alleged components contained nuclear fuel.

That distinction matters. Reactor parts without fuel would still be strategically sensitive if intended for a military nuclear-propulsion programme. Fuelled reactor systems would raise a separate set of proliferation and environmental concerns, including the possibility of radioactive contamination at the wreck site. At present, there is no public evidence confirming the presence of nuclear fuel on board.

The North Korean angle is plausible enough to warrant scrutiny because of the wider strategic context. By late 2024, Moscow and Pyongyang had already deepened their military relationship. North Korea had supplied Russia with munitions for use in the war against Ukraine, while North Korean military personnel were later reported in Russia’s Kursk region. Russia, in turn, has been suspected of offering Pyongyang advanced military or technical assistance. Nuclear submarine-related technology would represent a particularly sensitive form of support.

Several further details add to the opacity of the incident. Russian naval vessels were reported in the area, including Ivan Gren. Some accounts state that the Russian vessel did not rescue the crew from their lifeboat, while Spanish rescue services ultimately recovered the survivors. Reports also refer to red flares being fired.

After the sinking, additional activity was reportedly detected around the wreck site, which lies at a depth of around 2,500 metres. The Russian vessel Yantar, officially described as a research ship but widely associated with underwater intelligence and seabed operations, later appeared near the area. Further reported seabed explosions have led to speculation that Russia may have sought to destroy, obscure or recover sensitive material from the wreck. That version also remains unproven, but it is consistent with the level of secrecy surrounding the case.

The incident therefore presents two competing narratives. The official Russian version is that a sanctioned, defence-linked cargo vessel was attacked while transporting declared industrial cargo to Russia’s Far East. The alternative version is that the declared manifest may have concealed sensitive reactor components, possibly intended for North Korea, and that the sinking either interrupted or exposed a covert military transfer.

Neither version fully answers the available questions. What exactly was inside the empty containers? Why was a Russian defence-linked logistics vessel carrying such cargo through the Mediterranean? What caused the hull breach and the reported explosions? Why did the case re-emerge only after a later Spanish parliamentary document referred to submarine-type reactor components? And why did Russian underwater assets show such interest in the site after the sinking?

For now, the Ursa Major case remains an unresolved maritime incident with potentially serious strategic and environmental implications. The most significant claims — nuclear reactor components, a North Korean destination, and an external attack — have not been proven. Nor is there public evidence that any alleged reactor-related cargo contained nuclear fuel. Yet if sensitive nuclear or industrial material was on board, the sinking and reported subsequent seabed explosions would raise questions not only about proliferation and covert military logistics, but also about possible contamination risks in the Mediterranean. The convergence of a sanctioned Russian military logistics operator, unexplained cargo details, alleged reactor components, reported naval activity and Russia’s expanding relationship with Pyongyang makes the sinking more than a routine accident at sea.