BEIJING China wasted little time on Thursday protesting against embattled Japanese Prime Minister Taro Aso's remarks that disputed islands in the East China Sea belonged to his country.
It was the second time in three months that Sino-Japanese ties have been strained by the long-running dispute over the uninhabited islands, known as the Senkaku in Japan and the Diaoyu in China. The islands may lie near potential oil and gas reserves.
"China expresses strong dissatisfaction and has made a solemn representation to Japan," Chinese Foreign Ministry spokesman Ma Zhaouxu said in a statement on the ministry's website (www.fmprc.gov.cn).
The islands "have been China's territory since ancient times and China possess indisputable sovereignty," Ma said.
Aso had said in parliament earlier on Thursday that the islands were Japanese territory and thus covered by the Japan-U.S. security alliance, Japan's Kyodo news agency reported.
The Japanese leader is floundering in public opinion polls, stoking worries among lawmakers in his Liberal Democratic Party (LDP) that it could lose power after over a half-century of almost unbroken rule.
During Aso's time in power since September, Tokyo and Beijing have mostly maintained the steadier relations that emerged after years of rancour.
But the premier, a former foreign minister, has been an outspoken nationalist, wary of China and its regional ambitions.