The Air Self-Defense Force scrambled F-15 fighter jets after a Chinese aircraft on Saturday approached the Senkaku Islands in the East China Sea, the Defense Ministry reported.

However, the Y-12 propeller plane, operated by China’s State Oceanic Administration, did not intrude into Japanese airspace above the islet chain, whose sovereignty is vehemently disputed by Beijing, the ministry said.

It was the first Chinese aircraft spotted in the vicinity of the Japan-controlled islets since Dec. 26, and the sixth since Dec. 13, when a Chinese plane intruded into Japan’s airspace south of the Senkakus.

According to the ministry’s Joint Staff Office, the ASDF dispatched F-15 jets from its base in Naha, Okinawa Prefecture, after the Self-Defense Forces’ radar detected the Chinese propeller plane approaching the disputed isles from the northwest around noon Saturday.

The aircraft passed as close as 120 km north of the Senkakus, before steering eastward and then departing toward the north.