The bow of the 77 211-ton Alpha remained stuck into the stern of 25 836-ton Wan Hai. Parting them could sink both vessels, Coast Guard officials said.
The two ships continued to drift east at fice kilometres per hour, while the coast guard sent a tug boat to the scene.
The Wan Hai was on its way to Hong Kong with more than 1 000 containers on board when it collided with the Alpha Action, Jiji Press said.