A private boat carrying Taiwanese protesters and nine accompanying Taiwanese patrol vessels briefly entered Japanese territorial waters near a disputed island in the East China Sea on June 16 despite repeated warnings from Japan.

Chief Cabinet Secretary Nobutaka Machimura denounced the intrusion as "regrettable" but added that Taiwan and Japan "should act calmly" to avoid disturbing the regional peace.

The boats entered the Senkaku islands, which are controlled by Japan but claimed by Taiwan and China, and have been a frequent source of diplomatic tension.