Tense China-Japan relations could do without a new flashpoint. But it was predictable after Beijing set up an air defence identification zone across the East China Sea which encompasses islands over which the two countries dispute territorial possession. China has warned that it will take "defensive emergency measures" against aircraft that fail to identify themselves properly in airspace over them.
The Diaoyu Islands are a group of uninhabited islands located roughly due east of mainland China, northeast of Taiwan, west of Okinawa Island, and north of the southwestern end of the Ryukyu Islands. They are currently controlled by Japan, which calls them Senkaku Islands. Both China and Taiwan claim sovereignty over the islands.