BEIJING, March 12 (Xinhua) -- Chinese marine surveillance ships continued regular patrols in territorial waters surrounding the Diaoyu Islands on Tuesday, the State Oceanic Administration (SOA) said.

A fleet consisting of the Haijian 51, Haijian 23 and Haijian 27 spotted Japanese ships sailing in the waters. The fleet monitored the Japanese ships' movements and took photos of the vessels, an SOA statement said.

The marine surveillance fleet solemnly declared that the Diaoyu Islands have been Chinese territory since ancient times, and urged them to immediately leave the Chinese waters, the statement said.