The ships had been sailing in the contiguous zone near the disputed island chain in the East China Sea, but later entered the 12-nautical-mile band around them that come under Japan’s territorial waters.
The Chinese ships were in the contiguous zone for about half an hour starting at around 6:25 am on Sunday.
According to the Japan Times, two of the ships sailed into Japanese waters southeast of the islands of Kubajima, and the other two followed suit east of Minamikojima, the coast guard said.
The four surveillance ships have been cruising around the uninhabited islands since Friday.
The contiguous zone refers to a buffer area that extends a further 12 nautical miles beyond the territorial waters, the report said.
Tensions over the islands, known as Diaoyu in China and Tiaoyutai in Taiwan, have risen dramatically since Japan nationalized some of the islands on September 11.
The islands are said to be situated in rich fishing grounds and the seabed underneath may harbor vast mineral reserves.
According to the report, Japanese Prime Minister Yoshihiko Noda and Chinese Premier Wen Jiabao will not hold bilateral talks at the Asian and European leaders meeting in Laos next week, government sources said.
The Japanese and Chinese governments have decided against having bilateral talks at the two-day event from November 5 to 6 because the leaders would then have to take up the Senkaku dispute, which could backfire on both sides, the sources said.
Noda and Wen are also expected to avoid meeting on the sidelines of the Association of Southeast Asian Nations summit in Cambodia later in the month, it added.
Beijing: Four Chinese maritime surveillance ships were seen in Japan’s territorial waters around the Senkaku Islands on Sunday after ignoring warnings to stay clear, the Japan Coast Guard has said.
First Published: Monday, October 29, 2012, 16:30