A North Korean tanker has saved 21 crew members from a compatriot cargoship that sank in the Sea of Japan on 22 May.

Video footage showed the 6,800-dwt Chong Bong (built 1989) listing to starboard 48 km (30 miles) off Japan's Oki Islands and then later disappeared beneath the waves.

The day before, the vessel had made a request for help to Japan's Maritime Security Agency (MSA), reporting flooding in the hold, the Yonhap news agency said.

The crew boarded lifeboats as the list increased.

They were picked up by a tanker — the 1,200-dwt Yu Jong 2 (built 1986) — five hours later. No injuries were reported.

The MSA said it did not carry out any rescue activities as a result.

The Japanese organisation said the Chong Bong was en route from Chongjin to Songnim in North Korea with an iron cargo, adding that oil had been spotted in the area.

The MSA added that the weather was not particularly severe at the time of the accident.

The vessel is operated by Chongbong Shipping, according to Equasis.

Exporting North Korean coal?

In 2019, the US Office of Foreign Assets Control (OFAC) included the ship on a list of vessels believed to have exported North Korean coal since 2017.

But OFAC said the list did not show sanctioned vessels.

Japanese authorities are investigating the contents of the cargo.

The Chong Bong's last recorded port-state-control inspection was in 2015.

In 2014, the ship was detained in China twice.

The second time saw it held in Rizhao with 19 deficiencies.

Grounds for detention were related to crew certificates, fixed fire-extinguishing installations and lifeboats.