Four Chinese coastguard ships have reportedly entered disputed waters near the East China Sea islands and stayed there for two hours.
The incident took place after top leaders of the two nations had met on the sideslines of the G-20 summit.
News 24 reports that the ships entered the disputed maritime zone around Uotsurijima and stayed there for nearly two hours.
Uotsurijima is one of the five islands that have been the reason for the maritime dispute between Japan and China, the report added.
The incursion reports came after Japanese Prime Minister Shinzo Abe urged Chinese President Xi Jinping to resolve the issue of disputed islets that has strained the relations between Asia's two largest economies.
The top leaders of the two rival nations met for a short time on the sidelines of the in the G-20 summit.
