TikTok is thought to have about half a billion active users worldwide, with a large percentage in their teens or early 20s.

Axar.az reports citing BBC that the short-form video app has become a fertile birthing ground for memes, many of them music-related.

People - mostly under-20s - use the app to post 15-second videos. Many involve lip-synching to songs, comedy routines and/or unusual editing tricks. These are then made available to both followers and strangers. By default, all accounts are public, although users can restrict uploads to an approved list of contacts.

TikTok also allows private messages to be sent but this facility is limited to "friends". Anyone over the age of 13 can use it and there are parental controls.

Critics in the US warn the app has the potential to compromise users' privacy.

Alex Stamos, who is the former chief security officer of Facebook and now a Stanford professor, tweeted his concern after reports emerged of a clash between Bytedance's US and Chinese employees.

The deleted videos reportedly contained heavy kissing, suggestive dance moves, and political debate.

Others worry about the fact China requires its social-media apps to provide the state access to users' information.