South Korea has become one of Russia’s biggest fuel suppliers. Some shipments are arriving on sanctioned tankers.

By the end of summer, South Korea had become Russia’s second-largest supplier of petroleum products, and sanctioned tankers were among those used to ship the fuel, The Guardian reported.

Tankers made 14 voyages from several South Korean ports to Russia’s Far East in July and August, carrying 176,000 tons of fuel, mostly diesel, according to The Guardian.

Seven tankers plied the routes, three of them under British and EU sanctions. One, the tanker Chongchon, did not even enter South Korean ports: its fuel was transferred from another vessel at sea, a method that conceals the cargo’s origin.

In at least two more cases, sanctioned tankers loading at South Korean ports officially listed Japan as their destination but instead headed for Vladivostok. Exactly who owned and sold the fuel remains unclear.

Russia imported 368,000 tons of petroleum products by sea in August, with 112,000 tons supplied by South Korea. Only India supplied more fuel to Russia that month.

South Korea’s Foreign Ministry declined to comment on the shipments or the use of sanctioned tankers. It said only that Seoul “supports, and is actively taking part in, international efforts to help end the war in Ukraine and bring about a peaceful recovery.”

South Korea has supplied Ukraine with humanitarian aid since the full-scale war with Russia began, along with non-lethal military equipment such as body armor and demining vehicles, The Guardian reported. But Seoul is trying to balance its support for Kyiv against its desire to maintain good relations with Moscow, and has only partially joined Western sanctions, mainly through export controls on industrial equipment and high-tech goods.

The fuel shipments, amid a crisis in Russia caused by Ukrainian strikes on oil refineries, could expose Seoul as a “weak link” in Western efforts to pressure the Kremlin, The Guardian concluded.

The Guardian’s report on fuel shipments from South Korea to Russia came amid a diplomatic row between Seoul and Kyiv. At the U.N. General Assembly in late September, Volodymyr Zelensky said Ukraine had transferred to South Korea two North Korean soldiers captured in early 2025.

Seoul accused Zelensky of violating an agreement to keep the transfer secret, noting that Ukraine itself had originally insisted on the secrecy. South Korea demanded that Kyiv issue an official apology.

Today, South Korea’s foreign minister, Cho Hyun, said he had received an apology from his Ukrainian counterpart, Andrii Sybiha, but that its level was different “from the level we expect.” He said Seoul now intends to “take firm measures.”

The war in photos. Kharkiv