Sub Flees After Navy Chase

The fragile relations between Tokyo and Beijing were further weakened yesterday when a suspected Chinese nuclear submarine was chased out of Japanese territorial waters.

The submarine was detected about 180 miles south-west of Okinawa near the Senkakus, an island chain whose ownership is disputed.

It was the first time the Japanese navy had pursued an unidentified vessel since March 1999, when two suspected North Korean ships were seen off Japan's coast.

The submarine refused demands to surface and identify itself but reportedly left the area after three hours without a shot being fired. It was then chased through international waters by two destroyers and a helicopter.

Beijing would not be drawn on reports that the submarine was Chinese.

The Japanese prime minister, Junichiro Koizumi, described the encounter as "regrettable", adding: "It is certainly not a good thing that a submarine of unknown national origin entered our territorial waters."

Defence officials believe the vessel may have been among two Chinese military vessels spotted in the area this week.

The sighting comes at a delicate time for Sino-Japanese ties. The countries are at odds over gasfields near their maritime border in the East China Sea.

Beijing reacted angrily this week to a Japanese defence agency report saying China could attack if US troops on Okinawa were asked to help Taiwan in a possible conflict.