Japanese Coast Guard vessels fired water cannon to turn away about 40 Taiwan fishing boats and 12 Taiwan Coast Guard vessels. Six Chinese patrol ships were also near the islands but four left, leaving two nearby but not in waters Japan considers its own.

Japan protested to Taiwan, a day after lodging a complaint with China over what it called a similar intrusion by Chinese vessels.

Taiwan has friendly ties with Japan, but the two sides have long squabbled over fishing rights in the area. China and Taiwan both argue they have inherited China’s historic sovereignty over the islands.

The flare-up in tension comes at a time when both China and Japan confront domestic political pressures. Japanese Prime Minister Yoshihiko Noda’s government faces an election in months, adding pressure on him not to look weak on China. China’s Communist Party is preoccupied with the leadership turnover, with President Hu Jintao due to step down.