Beijing, China's top spy agency, on Monday warned air passengers not to open window blinds during takeoff and landing to take photographs at dual-use civil and military airports after a foreigner was found taking photographs from a mobile phone, according to a media report.

The Ministry of State Security, in a post on its official WeChat account, similar X, urged passengers to comply with instructions to close blinds during takeoff, landing and taxiing at dual airports.

They should not take unauthorized photographs or videos, nor upload the content to the Internet, he said, noting that the practice was "in line with the standard approach of countries around the world of maintaining secrecy around military installations," he said. the South China Morning Post, based in Hong Kong. reported.

The ministry said the warning was issued in reference to a recent case involving a foreigner, but gave no further details.

According to domestic media reports, a foreign national aboard a flight from the eastern Chinese city of Yiwu to Beijing earlier this month allegedly used a mobile phone to take photographs of a joint-use airport, and a fellow passenger reported the problem, after which the local officials alerted the police.

“Safeguarding national security is the responsibility and duty of every citizen. “Unauthorized filming of military facilities and equipment poses a serious threat to national security,” the ministry said, while calling on the public to cooperate in maintaining the security and confidentiality of joint-use airports.

In the WeChat post, the ministry said that joint-use facilities that make up nearly a third of China's airports generally deploy important military equipment and that passengers are not allowed to take photographs of sensitive military areas.

These airports are used for both civil aviation and regular air force training, and will be available for military use during times of war, the ministry said. In addition, many of them are located near coastal and border areas “showing prominent strategic positions and significant military value,” he noted.

In recent months, China has stepped up public security and security at its military facilities amid its intensified strategic rivalry with the United States and its allies, especially over the disputed South China Sea and Taiwan.

While China claims most of the South China Sea as its own, it also claims that the autonomous island of Taiwan is part of the mainland and vows to seize it.

The Philippines, Vietnam, Malaysia, Brunei and Taiwan have counterclaims over the South China Sea.