Facebook has admitted a design flaw in its Messenger Kids Service that exposed thousands of children on group chats with unauthorised users.

According to a report in The Verge on Tuesday, the design flaw "allowed users to sidestep that protection through the group chat system, thereby letting children to enter group chats with unapproved strangers".

The social networking platform introduced Messenger Kids in 2017 and is aimed at kids under 13 years of age. Despite call for withdrawal by experts, Facebook said a "technical error" was behind the problem in group chat. Facebook sent notification to parents, saying it has disabled the group chats in cases where the flaw was detected.

"We recently notified some parents of Messenger Kids account users about a technical error that we detected affecting a small number of group chats," a Facebook spokesperson was quoted as saying.

"We turned off the affected chats and provided parents with additional resources on Messenger Kids and online safety," the company added.

Messenger Kids is a video chat and messaging app designed for kids to communicate with family and close friends that parents or caregivers approve.

Parents set up and manage their child's Messenger Kids account through their own Facebook account.

It is unclear how long the bug was present in the app's group chat feature. Last year, more than 100 child health experts wrote an open letter to Facebook CEO Mark Zuckerberg, urging him to discontinue the Messenger Kids app.

"At a time when there is mounting concern about how social media use affects the well being of adolescents, it is particularly irresponsible to encourage children as young as pre-schoolers to start using a Facebook product," the authors wrote.

Facing the flak from lawmakers and experts, Facebook in February this year decided not to build a new app called "LOL" to let children share and post humorous meme content. Instead, the social media giant said it would focus more on its Messenger Kids service. (IANS)