CAMP HUMPHREYS, South Korea — The United Kingdom and South Korean navies patrolled the seas around the Korean Peninsula this month looking for illegal shipping into and from North Korea.

The first-of-its-kind joint patrol began on an unspecified date in April and concluded Thursday, according to a news release from the Ministry of National Defense. Surface ships from both countries and a South Korean maritime patrol aircraft took part in the mission.

The patrol shows “a firm commitment to strengthening … the implementation of UN Security Council sanctions resolutions to limit the financing of North Korea’s ballistic missile and nuclear programs,” the release said.

The release did not say whether any North Korean ships were interdicted. Neither countries defense ministries immediately responded to a request for comment by phone Thursday.

The two navies will “continue to strengthen” their efforts in enforcing sanctions against North Korea, the release added.

The patrol comes nearly four months after South Korean President Yoon Suk Yeol met with U.K. Prime Minister Rishi Sunak for a summit at Downing Street.

The leaders signed the Downing Street Accord, which condemned North Korea’s “unlawful nuclear and missile development” and said their countries will conduct joint patrols to uphold Security Council sanctions.

Canada in April 2023 deployed a warship and a CP-140 Aurora patrol aircraft to the Indo-Pacific region for six weeks of sanctions enforcement, dubbed Operation NEON, according to a Canadian Armed Forces news release at the time. The operation was extended in March 2023 for an additional three years.

New Zealand also dispatched a P-8A Poseidon reconnaissance aircraft to the region for sanctions enforcement from April to May, according to a New Zealand Defense Force news release Wednesday.

The Security Council’s sanctions require member states to inspect and seize ships in their waters that are suspected of illicitly trading with North Korea.

The communist regime is estimated to have imported over 1.5 million barrels of refined oil between January and September 2023 and is suspected of covertly supplying Russia with 1,000 containers of ammunition for the war in Ukraine, according to South Korea’s Foreign Affairs Ministry and the White House.

On March 28, U.S. Ambassador to the U.N. Linda Thomas-Greenfield proposed a Security Council resolution to renew the independent panel of experts to monitor sanctions enforcement against North Korea.

Russia vetoed the resolution, although 13 of the 15 member states approved of the plan; China abstained.