Japan's Coast Guard says 3 Chinese patrol ships temporarily entered Japanese territorial waters near the Senkaku Islands in the East China Sea on Tuesday.
Coast guard officials say the ships breached waters off Uotsuri Island of Okinawa Prefecture shortly after 10 AM.
The 3 ships remained there for about 90 minutes before moving to the contiguous zone just outside of Japanese waters by noon.
It is the 3rd day this year that Chinese government vessels have entered Japanese waters off the Senkakus.
The previous incursion was on January 15th.
Kenji Kanasugi, the director-general of the Foreign Ministry's Asian and Oceanian Affairs Bureau, lodged a protest with the Chinese Embassy in Tokyo.
He said intrusions into Japan's waters are an infringement of sovereignty.
Japan controls the Senkaku Islands. The Japanese government maintains the islands are an inherent part of Japan's territory. China and Taiwan claim them.