Beijing may be testing the patience of Prime Minister Shinzo Abe, who has recently kept his hawkish streak in check as he instead focuses on domestic economic measures.
On Monday and Tuesday, four Chinese maritime survey ships stayed inside Japan's territorial waters around the Japan-controlled Senkaku Islands in the East China Sea for more than 13 hours, the longest Chinese intrusion since September, drawing another strong protest from Tokyo.
Chief Cabinet Secretary Yoshihide Suga called the lengthy intrusion "extremely abnormal" and said the government lodged a "even stronger" protest with China over the repeated violations by its government ships into the territorial waters around the islets, which are claimed by Beijing, where the islets are known as the Diaoyu.