Chinese boats near disputed islands

A view of Senkaku/Diaoyu islands in the East China Sea

Japan's coastguard says two Chinese boats were spotted off islands at the center of a bitter dispute between Beijing and Tokyo in the East China Sea.

Two Chinese fishing patrol boats were sighted around 7:45 a.m. on Sunday (2245 GMT on Saturday) repeatedly trying to enter waters 44 kilometers off the disputed islands, Kyodo News reported, citing the Japanese coast guard. 

"They are still navigating off the Senkaku islands, and our patrol ships and airplanes are warning them by radio not to enter Japanese territorial waters," AFP quoted a coastguard official as saying. 

The two biggest economies of Asia both claim sovereignty over the cluster of small islands in the East China Sea. The uninhabited islands, called the Senkaku in Japan and the Diaoyu in China, are believed to have vast natural resources. 

The dispute over the ownership of the islands became heated in September when Japan detained a Chinese trawler captain near the chain after his vessel collided with two Japanese coastguard ships. 

The Chinese captain was held in custody for 17 days and then released. 

Several rival demonstrations have been staged in both China and Japan in recent weeks over the territorial dispute.