Two Chinese aircraft carriers have been seen operating in the Pacific at once for the first time, Japan’s Ministry of Defence has said.

China’s Shandong and four other vessels on Monday sailed within Japan’s exclusive economic zone (EEZ), the Defence Ministry said on Tuesday.

The aircraft carrier conducted landing and takeoff drills involving its fighter jets and helicopters in waters north of the Pacific atoll of Okinotori, the ministry said.

Tokyo’s announcement came a day after Japanese officials said the Liaoning, the older of China’s two operating aircraft carriers, had entered waters near the remote island of Minamitorishima.

Japanese Chief Cabinet Secretary Yoshimasa Hayashi said Tokyo would step up surveillance and had conveyed “an appropriate message” to China, without elaborating.

On Monday, Hayashi, who is Tokyo’s top spokesman, said China’s growing maritime activity appeared to be aimed at bolstering its capability to carry out missions farther from its shores.

Chinese Foreign Ministry spokesman Lin Jian on Monday defended the aircraft carriers’ movements, describing them as “fully consistent with international law and international practices”.

“Our national defence policy is defensive in nature. We hope Japan will view those activities objectively and rationally,” Lin told a regular news conference.