Japan scrambled F-15 fighter aircraft after a Chinese Government plane was spotted on course for a group of disputed islets, officials said Monday.
A Y-12 turboprop from China headed south over the East China Sea early Sunday, prompting the Japanese aircraft to take off from Okinawa, the Defence Ministry said.
It turned back toward China 100 kilometres before entering Japanese airspace, the ministry said. An official declined to say how many Japanese jets were scrambled.
The Japanese-administered Senkaku Islands are also claimed by China and Taiwan, where they are called Diaoyu and Tiaoyutai, respectively.
In November, China declared an air defence identification zone covering a wide area including the Senkakus, technically requiring other countries to notify Beijing before flying into the zone.