TENSION between Japan and China grew yesterday when an unidentified nuclear submarine sailed into Japanese waters.

The submarine, which had been tracked since Monday and whose nationality remains unknown, was widely suspected of being Chinese and triggered security action by Japan’s Marine Self-Defence Force (MSDF) for only the second time. Under the tightly worded Self-Defence Forces law, such action can be taken only when Japan is directly under threat.

The craft entered the seas off the coast of Miyako, one of the 600-mile-long chain of small Okinawan islands stretching from the southern tip of Japan. The area, which lies close to Taiwan, has been a recurring territorial flashpoint between Japan and China. Tokyo has recently lodged complaints with Beijing over Chinese research vessels and naval ships repeatedly appearing in Japan’s exclusive economic waters.

The latest intrusion comes as the two neighbours are locked in a bitter dispute over oil and gas drilling rights in the region. In addition, an influential Japanese defence panel recently leaked proposals for coping with a potential military attack by China. Beijing responded vehemently, describing the scenarios as “nothing less than an affront to China’s sovereignty and territorial integrity”.

As the submarine neared Miyako waters, a military aircraft was scrambled and demanded that the vessel either surface and show her flag, or leave immediately. The sub apparently moved out of Japanese waters shortly afterwards without identifying herself, and no warning shot was fired.

As a measure of the current tensions, the decision to alert MSDF units was made without the usual step of convening a Japanese Security Council meeting. Nevertheless, cabinet sources admitted that the step of invoking the SDF law was not taken until after the sub had left Japanese waters.

The last time the MSDF was called into action was in March 1999, when two vessels sailed close to the Noto Peninsula in the Sea of Japan.

Japan’s suspicions that the submarine was Chinese were based on the sighting of a submarine rescue vessel and a ship-towing boat belonging to the Chinese Navy off Tanegashima island late last week.If it emerges that the submarine was Chinese, the diplomatic strain between the two countries will be significant. Both are nursing grievances against the other: China is offended by the decision of Junichiro Koizumi, the Japanese Prime Minister, to visit the Yasukuni war shrine, and Japan remains outraged by the violence of Chinese football fans during the summer’s Asian Cup.

But underlying these are more serious showdowns over natural resources. The stakes were raised this year when China overtook Japan as the world’s second-largest con- sumer of oil after the US.

Tensions centre on the Japanese Senkaku islands, the ownership of which has long been a matter of dispute, and recent research showing that potential energy reserves are locked under a line dividing Japanese and Chinese waters.

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