China and the US have cracked down on illegal fishing activities in the Pacific Ocean during a combined naval operation, the Xinhua News Agency reported on Monday.

Two ships from China's Coast Guard (CCC) and the US Coast Guard vessel USS Mellon have been conducting operations since July, Xinhua reported.

A CCC official told Xinhua that the operations cracked down on illegal fishing and protected the fishing source in the high seas, and guided the development of the deep-sea fishing industry.

The official also said that cooperation between the two countries' coast guards has deepened through personnel exchanges and joint operations.

The CCC said it plans to expand patrols in the North Pacific Ocean and deepen cooperation with the US, Xinhua reported.

Beijing and Washington agreed on joint efforts in cracking down on illegal fishing in a memorandum signed in 1993 under a United Nations General Assembly resolution.

CCC also said 24 of its ships in the area have captured hundreds of boats accused of engaging in illegal fishing, 21 of them involved in drift-net activities, according to Xinhua.