Japanese media reports say Tokyo has scrambled F-15 fighter jets after a Chinese plane entered disputed airspace near contested islands in the East China Sea.
The reports quote Chief Cabinet Secretary Osamu Fujimura as saying the jets were sent in response to a Chinese Oceanic Administration airplane that was spotted near the islands on Thursday.
The uninhabited islands, known in Japan as Senkaku and in China as Diaoyu, have been the source of major tension between the two Asian powers.
Since Tokyo purchased the islands from a private landowner in September, China has sent regular patrol missions to the disputed waters, in what analysts say is Beijing's attempt to establish the fact that it can come and go as its pleases.
The Japanese Coast Guard says four Chinese maritime surveillance vessels were seen near the Japan-administered islands earlier on Thursday.