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.