Two Chinese aircraft carriers were observed operating in the Pacific Ocean at the same time for the first time, Japan’s Ministry of Defense said on Tuesday.

The ministry said the Shandong, accompanied by four other vessels, sailed within Japan’s exclusive economic zone (EEZ) on Monday.

The carrier conducted takeoff and landing drills using fighter jets and helicopters in waters north of the Pacific atoll of Okinotori, according to the ministry.

Separately, Japan said on Monday that the Liaoning, China’s older aircraft carrier, had entered waters near the remote island of Minamitorishima.

Chief Cabinet Secretary Yoshimasa Hayashi said Tokyo had delivered “an appropriate message” to China regarding the activities, though he did not provide further details.

Hayashi, speaking as the government’s top spokesperson, also said China’s maritime operations appeared aimed at expanding its ability to carry out missions farther from its coastline.

In response, Chinese Foreign Ministry spokesman Lin Jian defended the deployment, calling the carriers’ movements “fully consistent with international law and international practices.”

“Our national defense policy is defensive in nature. We hope Japan will view those activities objectively and rationally,” Lin said at a regular press briefing.