Three Chinese patrol vessels have entered into disputed waters in the East China Sea sparking fresh tensions in the territorial crisis with Japan.
This is the first such episode since Japanese Prime Minister Shinzo Abe and Chinese President Xi Jinping held talks on the sides of the Apec summit in Beijing recently.
The Japanese coast guard has said the Chinese boats briefly entered the waters near the chain of islands - known as Senkaku in Japan and Diaoyu in China – at about 10am local time (25 November).
Despite warnings from Tokyo's naval authorities, the vessels sailed in the waters for nearly two hours before leaving the region, say the Japanese.
Junichi Ihara, the Japanese foreign ministry's Asian and Oceanian Affairs Bureau Chief, has lodged a formal protest with Han Zhiqiang, a senior Chinese authority working in the embassy in Tokyo.
The latest event echoes similar incidents in the past as the two countries continue to quarrel over ownership of the archipelago.
Nearly 30 such episodes have taken place this year with the last one on 3 November.
Tensions were at peak when Japan announced they were buying the uninhabited islands from private owners in 2012.