The US Army has banned the use of the increasingly popular TikTok app on work mobile phones for security reasons.
The app, owned by the Chinese company, ByteDance, has come under close scrutiny recently in the US and other countries.
US Army spokeswoman, Lt Col Robin Ochoa, told US media it was considered "a cyber threat".
The app allows its more than half a billion users worldwide to post short, often quirky, self-edited videos.
TikTok is a draw for its mainly young users attracted by the ability to make and share 15-second videos, such as lip-synching to songs and comedy skits.
All accounts are by default public, though subscribers have the ability to restrict this.
Col Ochoa told Military.Com that the Army had advised its personnel to stop using the app on government-owned phones from the middle of December. It follows a similar move by the US Navy.
The military cannot prevent its use on private phones but the Department of Defence recently issued guidance for employees "to be wary of applications you download".
Lawmakers have voiced concerns that the app can be used to collect US citizens' data and poses a risk to national security because it could be forced to co-operate in Chinese intelligence gathering.
Democratic and Republican senators called in October for an investigation by intelligence agencies into the national security risks posed by TikTok.
Arkansas Senator Tom Cotton suggested that TikTok could also be used for a foreign-influence campaign similar to that carried out on social media in the 2016 US presidential election.
In its defence, TikTok said recently that all US user data was located outside China, and not subject to Chinese law. It also had strong policies on cyber-security and data privacy.
Speaking to the BBC in November, TikTok said that changes made over the course of 2019 included strengthening the capabilities and autonomy of the US team.
TikTok also hired a company to carry out an audit to make sure users' data is not sent to China using third-party apps that can plug into the app.