Chinese surveillance ships on Sunday entered the contiguous zone just outside Japan's territorial waters around the disputed Senkaku Islands for the 30th straight day, the coast guard reported.
The coast guard said four of China's surveillance vessels, which have been sailing near the Japan-controlled Senkaku islet chain in the East China Sea since Nov. 7, left the contiguous zone in the early morning but four new Chinese ships then entered the waters.
When a coast guard cutter warned the four new vessels not to stray too close to Japan's territorial waters, one of the ships responded via radio that the Senkakus are an inherent part of Chinese territory, according to the 11th Regional Coast Guard Headquarters in Naha, Okinawa Prefecture.
China lays claim to the uninhabited islets, which it calls Diaoyu, along with Taiwan, which refers to them as Tiaoyutai.