TOKYO (Reuters) - A Chinese navy reconnaissance vessel briefly entered Japan's territorial waters early Wednesday off the southwestern prefecture of Kagoshima, a Japanese government spokesman said.

Deputy Chief Cabinet Secretary Hiroshige Seko said the vessel had been spotted by a Japanese patrol plane around 3:30 a.m. local time and that it had left around 5 a.m.

"The government will continue to take all possible measures for warning and surveillance activity for our territorial waters and airspace," Seko told a news conference.

Last week, Japan summoned the Chinese ambassador to express concern after a Chinese navy ship sailed close to what Japan considers its territorial waters in the East China Sea for the first time, increasing tensions over the disputed area.

(Reporting by Kaori Kaneko; Editing by Michael Perry)