Users will be able to integrate their Instagram accounts with Facebook's dating profile and add Instagram followers to their "Secret Crush" lists.

That feature allows users to indicate romantic interest in a friend, without the attraction becoming public.

If two friends each tag the other as a crush, Facebook Dating alerts both of the interest.

The service would be optional for Facebook and Instagram users, the company said, adding that dating activity of users will not appear on their profile or news feed.

The launch marks a major expansion of Facebook's dating service, initially rolled out in Colombia, Thailand, Canada, Argentina and Mexico last year.

It also opens the company to further scrutiny of its privacy and safety record, which has caught the attention of regulators around the world.

Facebook notes in the liability section of its terms of service that it does not conduct background checks or sex offender register searches.

"You interact with other users at your own risk," the terms state.

Australian Associated Press