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.