A Chinese cargo ship collided with an anchored freighter and sank off South Korea's west coast on Monday, killing at least three Chinese crew members, the coast guard said.

The 2,972-ton Chinese ship, carrying iron ore, was entering the port of Incheon, west of Seoul, when it slammed into an anchored South Korean vessel, a coast guard statement said.

The Chinese vessel sank immediately. A nearby vessel rescued five of the 17 crew members. Three crew members were later found dead and nine were missing, the coast guard said.

The South Korean cargo ship sustained minor damage and its crew was safe, the coast guard said.