Photo/IllutrationThe Asahi Shimbun

Maritime Self-Defense Force vessels have been patrolling international waters off the Korean Peninsula since late last year to thwart attempts by North Korea to evade international sanctions, government sources said.

Their primary task is to foil efforts by North Korea to acquire refined petroleum products from foreign cargo carriers in the Yellow Sea as well as the Sea of Japan.

U.N. sanctions slapped against Pyongyang for its nuclear and missile development programs ban exports of oil and oil-related products to North Korea.

It is the first involvement by MSDF vessels in efforts to bolster the effectiveness of U.N. sanctions.

China is strongly opposed to MSDF vessels operating in the Yellow Sea that rings its eastern coastline, but the Japanese government decided the patrols were necessary to ensure that the embargo remains watertight.

The MSDF monitors the movement of foreign ships and share that information with the United States, the sources said.

In the Sea of Japan, the SDF and the U.S. military patrol together, each in an assigned area.

The mission is purely aimed at “warning and monitoring" activities in waters surrounding North Korea, the sources added.

The MSDF vessels are not authorized to forcibly inspect suspect ships. Under the U.N. Security Council resolution, member nations are requested to inspect ships if they are suspected of transporting banned items.