They say the vessels intruded into Japan's waters off Minamikojima Island a little past 4 a.m. on Monday. The officials say the two ships were among three Chinese government vessels earlier seen navigating in the contiguous zone, just outside Japan's territorial waters.

They say the two ships were getting close to two Japanese fishing boats operating off Minamikojima around 4:20 a.m. They say Japanese patrol ships were sent to accompany the fishing boats and ensure their safety.

The officials say that as of 9 a.m., one of the two Chinese vessels was spotted 3 kilometers west-southwest of Uotsuri Island, and the other 4 kilometers south-southeast of the island. They also say two other Chinese government vessels are navigating in the contiguous zone.

This is the 11th time this year that official Chinese vessels have entered Japan's territorial waters off the Senkaku Islands.

Japan controls the islands. China and Taiwan claim them. The Japanese government maintains the islands are an inherent part of Japan's territory, in terms of history and international law. It says there is no issue of sovereignty to be resolved over them.