The maritime surveillance vessels entered the 12-nautical-mile zone around Uotsurijima, the main islet in the disputed chain called the Senkaku Islands in Japan and the Diaoyu Islands in China at about noon (0300 GMT).

Chinese vessels have moved in and out of what Japan says is its sovereign territory over the past two months since Tokyo nationalised some of the islands in the group.

On Friday, six Chinese government ships temporarily entered the territorial waters around the same islet, according to the coastguard.

As well as the potential mineral reserves, national pride is at stake in the decades-old spat, which has recently spiked and hit the huge trade relationship between the two biggest economies in the region.

Japan and China are readying for a third round of talks on the issue, but Japanese Prime Minister Yoshihiko Noda is not likely to hold bilateral talks with Chinese Prime Minister Wen Jiabao on the sidelines of an Asia-Europe summit in Laos opening on Monday, reports have said.