A blacklisted North Korean ship is under surveillance as it sails near South Korean waters, the country's Coast Guard said Thursday.

It said Orion Star freighter is presently sailing in waters near the port city of Yeosu, in the South Sea. The city is some 455 kilometers southwest of Seoul.

The ship is one of 31 vessels belonging to North Korea's Wonyang Shipping Corp. that has been blacklisted by U.N. Security Council Resolution 2270.

The council adopted the resolution earlier this month, imposing the harshest sanctions yet on North Korea, to punish it for its fourth nuclear test in January and long-range rocket launch last month.

The ship, which departed from the Nampo port near Pyongyang on Tuesday, is known to be bound for the communist country's northeastern port of Chongjin. It is expected to arrive at the port around Sunday at 7 p.m. if it maintains the current speed and heading.

Since the ship entered regions regulated by South Korea at around 11:45 a.m., the Coast Guard dispatched two cutters and is closely monitoring the ship's progress in line with the foreign ministry's policy directive.

Authorities said some 20 North Korean crew members are presumed to be on the 2,389-ton vessel, shipping some 3,600 tons of anthracite.

The ship itself is registered as Mongolian via a practice called flag of convenience that aims to avoid taxes and other regulations.

Under the sanctions, several North Korean vessels have reportedly turned back after being denied entry at Russian and Chinese ports, while another ship was impounded in the Philippines. (Yonhap)