Russian ships have supplied North Korea with oil on at least three occasions since the U.N. slapped various sanctions on the communist country, according to a report Friday from Reuters.

The sale of oil from Russia violates sanctions leveled against North Korea over the isolated country’s nuclear program, two Western European security sources told reporters. Russia is a major oil exporter across Europe and holds veto power within the UN security council.

“Russian vessels have made ship-to-ship transfers of petrochemicals to North Korean vessels on several occasions this year in breach of sanctions,” one of the sources said on condition of anonymity.

Another source independently confirmed the cargo ship-to-cargo ship trade did take place but noted that there was no evidence the Russian government was responsible for the transaction.

“There is no evidence that this is backed by the Russian state, but these Russian vessels are giving a lifeline to the North Koreans,” the second security source said.

North Korea is heavily reliant on imported fuel to prop up its beleaguered economy. The country also requires oil for its long-range ballistic missile and nuclear program that the U.S. argues destabilizes Asia.

Russia is not the only country being scrutinized for helping North Korea. Satellite images caught Chinese vessels selling oil to North Korean ocean-going ships more than 30 times since the end of October. The location of the trade, which took place in the West Sea on China’s border, was chosen presumably to avoid detection from South Korea.

“We need to focus on the fact that the illicit trade started after a UN Security Council resolution in September drastically capped North Korea’s imports of refined petroleum products,” a South Korean official told reporters Thursday.

U.N. Resolution 2375 forbids ship-to-ship trade with North Korea, yet violations do occur because it is nearly impossible to detect violators absent a Chinese crackdown on smugglers. Sanctions were slapped on the isolated communist country in September.

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