This undated photo, captured from a report released by the U.N. Panel of Experts that monitors the implementation of North Korean sanctions by U.N. member states, shows the locations of North Korea's illegal ship-to-ship transfers of banned items in 2023. Yonhap

A North Korean cargo ship suspected of smuggling out North Korean coal collided with a Chinese ship and sank in the Yellow Sea last month, according to a source familiar with the matter Thursday.

The accident is believed to have left around 15-20 North Korean crew members dead. But North Korea and China seem to be keeping a low-key stance about the accident, apparently due to a violation of United Nations Security Council (UNSC) sanctions banning exports of North Korean coal.

While turning off its automatic identification system (AIS), a North Korean cargo ship suspected of carrying coal sailed in the Yellow Sea in late February and sank after colliding with a Chinese vessel in waters near a southeastern Chinese port, according to the source.

Despite rescue operations by Chinese authorities, only a few North Korean crew members were saved, and nearly 20 are believed to be dead. The Chinese ship reportedly sustained minor damage.

At that time, it is believed that heavy fog made it difficult to secure visibility in the body of water where the accident occurred, the source said.

North Korean ships frequently turn off AIS, which transmits location and speed data to relevant authorities, in a bid to evade UNSC sanctions. The body of water where the accident took place is believed to be a route that North Korean cargo ships use to export coal.

UNSC Resolution 2371, adopted in 2017, imposed a blanket ban on overseas sales of North Korean coal, iron ore, other mineral resources and seafood.

"The North Korean ship appears to be overly loaded with coal. The cargo and ship sank altogether," the source said, adding China does not appear to want the accident to be known as it probably connived in North Korea's violation of the UNSC sanction.

In March 2017, a North Korean cargo ship collided with a Chinese vessel and sank near China's Lianyungang port. All of those aboard were saved, and China's transportation ministry announced the accident at that time. (Yonhap)