Japan's defence minister yesterday called for efforts to establish the intentions of an extraordinarily large group of about 10 Chinese warships and submarines that passed through international waters near Okinawa last weekend.

The comments by Toshimi Kitazawa highlight concerns in the Japanese security establishment about China's rapidly growing naval power and its implications for long-standing disputes over maritime territory and resources between east Asia's premier powers.

A Japanese official said the passage of the Chinese naval vessels followed an “extremely dangerous” incident in the East China Sea last week in which a ship-based Chinese helicopter came within 90 metres of a Japanese destroyer. Tokyo had protested about the manoeuvre “through diplomatic channels”, the official said.