Chinese maritime authorities launched a search for six seamen from the Democratic People's Republic of Korea (DPRK) Wednesday who are missing after their cargo ship sank off China's coast.

Altogether 20 DPRK crew members were aboard the vessel when it sank in strong winds about 90 nautical miles southeast of Dalian, in northeast China, at noon on Tuesday, said Zheng Jian, of the Ministry of Transport's Rescue and Salvage Bureau.

The ministry's Beihai Rescue Bureau immediately dispatched a helicopter to the area after receiving an SOS signal from the ship, and rescuers picked up one survivor two hours later, Zheng said.

The rescued seaman said 14 colleagues on two life rafts had been swept away by waves.

The Beihai Rescue Bureau also sent two rescue vessels to the area, and rescuers saved another 13 sailors from a raft late Tuesday afternoon, Zheng said.

"We are still searching for another raft and the other six crew members," he said.

The cargo ship was en route from the DPRK port city of Nampo to Dalian when it sank, he said.