SEOUL,  (UPI) — The United Nations Security Council sanctions are hitting North Korean ships.

The 27 vessels under the North Korean flag blacklisted under Resolution 2270 are all stranded at ports, Voice of America reported.

Two of those ships, according to AIS, a shipboard broadcast system, are moving between Nampo and Wonsan, but is not sailing to other countries.

Under U.N. sanctions, all ships under North Korea’s Ocean Maritime Management Company are marooned at various ports.

Three other North Korean ships, including the Sebo, the Mirim and the Hoeryong were stranded at the port of Nampo, and Mirim-2, Ranam-2 were among six vessels that were last seen headed for North Korea’s western coast, but since March have disappeared from radars, according to MarineTraffic.

VOA reported it’s likely some of the ships at Nampo have not left the port. Other ships, including the Chol Ryong, the Kang Gye and Ji Hye San were last seen headed for the North Korean eastern port of Wonsan, but in early April some of the ships were seen at Kimchaek, a eastern port city in North Hamgyong Province with the Tae Pyong San, another North Korean vessel.

More ships have been disappearing from radars since the adoption of Resolution 2270. Within 24 hours of the adoption of sanctions, 15 North Korean vessels could be tracked, but within four days that number was down to seven. In late March, only 2-3 ships could be picked up on radars.

In March China confirmed four North Korean ships have been removed from the U.N. blacklist, because they were not connected to OMM.