Three Chinese maritime surveillance ships sailed inside Japanese territorial waters near the disputed Senkaku Islands in the East China Sea on Thursday morning, according to the Japan Coast Guard.

It is the first time in four days that Chinese government ships have entered Japanese waters. The Chinese vessels entered the waters shortly after 7 a.m. and remained there until around 9:20 a.m.

Shinsuke Sugiyama, director general of the Japanese Foreign Ministry's Asian and Oceanian Affairs Bureau, lodged a protest by phone with Han Zhiqiang, Chinese minister-counselor to Japan, who reiterated China's claim over the sovereignty of the islands.