TOKYO (AP) — Japan’s defense chief Friday called for the bolstering of its anti-drone capability after a drone footage posted on Chinese social media showed a Japanese aircraft carrier docked at a restricted navy port west of Tokyo. Defense Minister Minoru Kihara called it a serious security threat.

Kihara's acknowledgement of the vulnerability comes more than a month after a video filmed by a drone showed JS Izumo, one of two Japanese helicopter carriers, being retrofitted to carry stealth fighters to strengthen Japan's counter-strike capability in the face of China's assertive military actions in the Indo-Pacific.

The footage, also showing plants, buildings and other facility at the Japan Maritime Self-Defense Force's Yokosuka naval base was posted on a Chinese social media site in March, prompting investigation by ministry officials. The footage has also been posted on other platforms such as X.

“After the video analysis we have reached a conclusion that the footage was most likely filmed by a flying drone," Kihara told reporters.

“We are taking the findings extremely seriously,” the minister added. “If drones harm defense facilities, it could cause serious disruptions to the defense of our country.”

Kihara declined to comment how the drone was able to fly over the flattop undetected, citing security reasons. But he stressed the need to respond to rapid technology advancement of drones and other unmanned vehicles. He also vowed to fortify defense around military bases.

He said Japan will accelerate effort to introduce more capable anti-drone equipment and strengthen counter measures such as forcible landing of drones by jamming.

The development comes at a time Japan is accelerating its military buildup to focus on its counter-strike capability with long-range missiles under the ongoing security strategy adopted in 2022. JS Izumo serves a key role in that strategy.

In 2015, a small drone laced with traces of radiation was found on the roof of the prime minister’s office, sparking concerns about drones and their possible use for terrorist attacks. There was no injuries or damage from the incident but its owner was convicted of obstruction of business.

Drone flights have since been restricted above key public and diplomatic areas as well as nuclear power facilities. While drones are used widely for industrial, search and rescue and security purposes, the number of violations by them have also rapidly increased.