Just months after building mini-games into Messenger, Facebook is reportedly preparing 'Instant Games' for the popular chat app.

Basketball, soccer and chess mini-games appeared in Messenger earlier this year, with users taking turns to set scores or play against a friend.

Facebook is now set to open Messenger up to third-party developers, though it appears they will be restricted to producing turn-based games.

HTML5 is said to be the technology behind Instant Games, as Facebook looks to maximise compatibility with a variety of devices.

Shuffle Cats Mini, a game by Candy Crush developer King, is reportedly in testing with New Zealand users.

It remains to be seen if Facebook will allow developers to integrate in-game purchases or advertising, though both would certainly boost the social network's bottom line.

Regardless, a potentially high-volume gaming platform should keep users coming back to Messenger as Facebook continues to extend the functionality of the standalone app.