The Chinese ship was spotted in the waters about 230 kilometres north-northeast of Taishojima, part of the Senkaku chain in the East China Sea, at around 6.30am, according to the JCG's 11th regional headquarters in Naha, the capital of Okinawa.
The research ship went out of the Japan-China median line at about 1.20pm after it was asked by a JCG patrol ship by radio to stop operating.
[Copyright The Jiji Press, Ltd.]