TOKYO A Japanese navy destroyer made a rare entry into China's territorial waters near Taiwan earlier this month without notifying China, prompting Beijing to lodge an official complaint.

The Japan Maritime Self-Defense Force's destroyer Suzutsuki sailed into China's waters off Zhejiang province on July 4, where China had said it would conduct naval drills, Kyodo news agency reported on Wednesday, citing diplomatic sources.

Suzutsuki, tasked with monitoring Chinese missile exercises in the East China Sea north of Taiwan, entered the waters without notifying China, broadcaster NTV reported, citing sources in Japan's defence ministry.

The destroyer sailed within 12 nautical miles (22km) of the Zhejiang coast for about 20 minutes despite warnings from Chinese vessels, and Beijing expressed "serious concerns" to Tokyo, Kyodo said.

Japan's defence ministry has launched an investigation questioning the captain of the Suzutsuki, and the crew's intention remains unclear, Kyodo said.

Chinese foreign ministry spokesperson Lin Jian told a regular news briefing on Thursday that China had lodged representations to the Japanese side regarding the "illegal and improper actions" of the Japanese ship.

The Japanese side explained that it was a technical error, Jian said.

China's coast guard and naval vessels have entered Japan's territorial waters, including June last year when Tokyo lodged a protest against Beijing after the Chinese navy sailed into Japanese waters near Yakushima island.

In December, the Chinese military said a US Navy ship "illegally" entered waters adjacent to a disputed South China Sea atoll that has recently seen several maritime confrontations with neighbours including the Philippines.

  - Reuters