Oil from South Korea being shipped to Russia as Ukraine war grinds on

Exclusive: Guardian analysis finds more than 150,000 tonnes of fuel was shipped to Russian ports in July and August, some using sanctioned tankers

Oil is being shipped from South Korea to Russia via sanctioned tankers as Moscow scrambles for supplies amid the war in Ukraine, a move one expert said “undermines” Seoul’s public backing for Kyiv.

Three of the vessels were under sanctions by the UK and EU, and one took on its cargo through a ship-to-ship transfer in South Korean waters – a method that can obscure where a cargo came from and lets ships avoid calling at port terminals.

Seoul has sent Ukraine humanitarian aid and non-lethal military supplies such as helmets, body armour and demining vehicles, and in 2023 pledged $2.3bn in support, most of it in loans.

While the fuel trade involves vessels sanctioned by some of Seoul’s western partners, it does not appear to breach South Korean law. South Korea’s own measures against Russia rely mainly on export controls on goods such as industrial machinery, electronics and vehicles.

It is unclear who owned or sold the fuel, which South Korean port records do not show.

Another sanctioned tanker, the Russian-flagged Astoria, which is also under Australian sanctions, loaded nearly 11,000 tonnes of fuel at Ulsan on 1 August, declaring Japan as its destination, before sailing to Vladivostok.

The third sanctioned tanker, the Chongchon, never berthed. It took on about 26,000 tonnes of fuel from an unsanctioned tanker, the Celeste I, at an anchorage off the southern South Korean port of Yeosu in early August, then headed to Vladivostok after declaring Singapore as its destination.

Russia’s capacity to refine oil has been severely disrupted by Ukrainian drone strikes. Its refinery throughput fell in June to its lowest level in more than 20 years, and diesel output is down nearly 30% on last year, according to the International Energy Agency.

According to data from the maritime analytics firm Kpler, the buyers included Rosneft, Russia’s state-controlled oil company, which is under UK, US, EU and Australian sanctions, and NNK, a Russian oil group whose owner, Eduard Khudainatov, and one of its companies, NNK-Oil, are under UK sanctions.

Loadings at South Korean ports began to surge in July, just as the country’s president, Lee Jae Myung, pledged $100m for Ukraine’s reconstruction at a Nato summit in Turkey.

In March, as the war with Iran shut the strait of Hormuz, South Korea capped exports of certain fuels and imported Russian naphtha under a US sanctions waiver.