Japan's ambassador to Beijing has returned home for talks on growing tensions over disputed islands in the East China Sea.
The BBC reports Japan twice lodged protests last week after Chinese boats entered what it considers to be its territorial waters around the islands, known as Senkaku in Japan and Diaoyu in China. T
The islands, which are uninhabited, are claimed by both countries and also Taiwan.
Japan said last week it was considering a plan to buy them from their private owners.
Three Chinese fishery patrol ships entered the waters near the islands last week.
Chief cabinet secretary Osamu Fujimura said in Tokyo that they eventually left, but two were still close by and Japanese patrol ships were keeping close watch.