A North Korea-flagged tanker was caught violating UN sanctions as it engaged in what is believed to be a ship-to-ship transfer of fuel with an unidentified ship on March 2.

The illicit operation was documented by a Royal Navy frigate which was operating in the East China Sea in cooperation with Japan, enforcing the UN sanctions against North Korea.

“North Korea-flagged tanker Saebyol, which was transmitting on ship tracking systems as a fishing boat, was spotted alongside a vessel of unknown nationality on the high seas, conducting a prohibited ship-to-ship transfer,” the navy said in a statement.

Evidence of the operation was gathered and reported to the United Nations.

Japan’s Ministry of Foreign Affairs noted that the the United Nations Security Council designated Saebyol as a vessel subject to assets freeze in March 2016.

“Sanctions evasion helps facilitate North Korea’s nuclear weapons program and is a major source of funding,” UK Defence Secretary, Gavin Williamson, said.

“Sanctions will remain in place and we and our partners will keep enforcing them until we see concrete steps towards North Korea’s complete, verifiable and irreversible denuclearisation.”

In a similar operation in May 2018, another Royal Navy ship observed and reported a Panama-flagged vessel conducting a prohibited ship-to-ship transfer with a North Korean-flagged vessel. This resulted in the Panamanian vessel being designated by the UN, deflagged and banned from port entry.

North Korea is subject to increased sanctions following several tests of nuclear warheads in 2016 and 2017. In September 2017, U.S. President Donald Trump issued an executive order on imposing additional sanctions against the country. The widened sanctions targeted the country’s shipping industry, trade, ports, and manufacturing, while a blockade was imposed on owning, controlling, or operating any port in North Korea, including any seaport, airport, or land port of entry.

In the latest step against North Korea’s sanctions evasion, the U.S. Department of the Treasury’s Office of Foreign Assets Control (OFAC) designated two China-based shipping companies that have helped North Korea evade sanctions.

In a related action, OFAC, along with the U.S. Department of State and the U.S. Coast Guard, has updated the North Korea shipping advisory, adding dozens of vessels that are believed to have engaged in ship-to-ship (STS) transfers with North Korean tankers or exported North Korean coal.