BEIJING, Sept. 8 (Xinhua) -- China Tuesday expressed grave concern over collisions between two Japanese patrol boats and a Chinese fishing boat in waters off the Diaoyu islands.

Foreign Ministry spokeswoman Jiang Yu reiterated that the Diaoyu islands, in the East China Sea between China and Japan, have belonged to China since ancient times.

The islands are 120 nautical miles northeast of Taiwan, 200 nautical miles west of China's mainland and 200 nautical miles east of Japan's southernmost island Okinawa.

Geologically the islands are attached to Taiwan. The waters around the islands are 100 to 150 meters deep and there is a 2,000-meter-deep oceanic trench between the islands and Japan's Okinawa islands.

Fishermen from China's Taiwan and Fujian and other provinces conducted activities such as fishing and collecting herbs in this area since ancient times.

The islands appeared on China's map since the Ming Dynasty (1368-1644).

There are records about the islands in a book published during the rule of Yong Le (1403 to 1424) in the Ming Dynasty, more than 400 years before Japan claimed discovery of the Diaoyu islands in 1884.