evidence: Ties between China and Japan have been strained by a territorial row over a group of islands, known as the Senkaku islands in Japan and the Diaoyu islands in China. [...] At the heart of the dispute are eight uninhabited islands and rocks in the East China Sea. They have a total area of about 7 sq km and lie north-east of Taiwan, east of the Chinese mainland and south-west of Japan's southern-most prefecture, Okinawa. The islands are controlled by Japan. [...] But this angered China, triggering public and diplomatic protests. Since then, Chinese government ships have regularly sailed in and out of what Japan says are its territorial waters around the islands.