Fourteen voyages ran from several South Korean ports to the Russian Far East, according to the report. Some of the vessels listed false destinations.
The tanker Layla carried a total of 57,000 tonnes of diesel from the port of Ulsan to Vladivostok over two voyages. Before the second, it told South Korean authorities its destination was the Japanese port of Niigata. The sanctioned, Russian-flagged Astoria loaded almost 11,000 tonnes of fuel in Ulsan on August 1, also declared Japan, and arrived in Vladivostok.
The tanker Chongchon took on about 26,000 tonnes of oil products at sea from the vessel Celeste I near the port of Yeosu. Its documents listed Singapore as the destination, but the tanker headed to Vladivostok.
The port documents reviewed by journalists do not establish who owned or sold the fuel. According to the analytics firm Kpler, buyers of the oil products delivered to Russia included Rosneft and the NNK group. NNK owner Eduard Khudainatov and the company NNK-Oil are on Britain's blacklist.
In August Russia imported 368,000 tonnes of oil products by sea, roughly seven times more than in July. According to estimates by the Finnish Centre for Research on Energy and Clean Air (CREA) based on Kpler data, that is the highest monthly figure since the start of Russia's full-scale invasion of Ukraine. South Korea accounted for 112,000 tonnes, or 31% of August imports; only India supplied more in that period.
The rise in supplies coincided with a fuel crisis in Russia after Ukrainian strikes on oil refineries. According to the International Energy Agency, Russia's oil refining volume fell in June to its lowest level in more than 20 years, and diesel output dropped by almost 30%. Russia banned the export of gasoline and diesel, extended tax breaks to imported fuel and allowed the sale of Euro-2 and Euro-3 gasoline. In mid-September, according to the service gdebenzin, AI-92 was unavailable at almost 45% of Russian filling stations and AI-95 at 53%.
CREA analyst Isaac Levi told The Guardian he was shocked that tankers under EU sanctions loaded fuel at South Korean ports and delivered it to Russia. In his view, this undermines the sanctions regime and South Korea's support for Ukraine. South Korea's Foreign Ministry declined to comment on the supplies or the use of sanctioned tankers, limiting itself to a statement of support for international efforts to end the war in Ukraine.
The Guardian's report was published amid a diplomatic scandal between Seoul and Kyiv. At the end of September, at the UN General Assembly, Volodymyr Zelensky said Ukraine had handed over to South Korea two North Korean servicemen captured in early 2025. Seoul accused Zelensky of violating agreements on non-disclosure, said it was demanding an official apology, and on October 6 received one from Ukrainian Foreign Minister Andrii Sybiha. South Korean Foreign Minister Cho Hyun said the level of apology did not meet expectations and that Seoul intended to take decisive measures.