The logo of the Chinese app ZAO, which allows users to swap their faces with celebrities and anyone else, is seen on a mobile phone screen in front of an advertisement of the app.

The app’s surge in popularity and sudden backlash from some users highlights how artificial intelligence (AI) technologies bring about new concerns surrounding identity verification.

ZAO was uploaded to China’s iOS App Store on Friday and immediately went viral. According to a post from the app makers on China’s Twitter-like Weibo, ZAO’s servers nearly crashed due to the surge in traffic.

ZAO was the most-downloaded free app in China’s iOS App Store as of 1 September.

Consumers sign-up for ZAO with their phone number and upload images of their face, using photographs taken with their smartphone.

They can then choose from a range of videos of celebrities on which to superimpose their face, and share the videos with their friends.

In addition to Chinese celebrities, other famous faces on the app include Leonardo DiCaprio and Marilyn Monroe.

However a section of the user agreement stated that consumers who upload their images to ZAO agree to surrender the intellectual property rights to their face, and permit ZAO to use their images for marketing purposes.

Zao said on Weibo that it would address those concerns.

“We thoroughly understand the anxiety people have toward privacy concerns”, the company said. “We have received the questions you have sent us. We will correct the areas we have not considered and require some time.”