Elon Musk spent the weekend further alienating Twitter users with more drastic changes to the social media giant, and he is facing a new challenge as tech nemesis Mark Zuckerberg prepares to launch a rival app this week.

Zuckerberg's Meta group, which owns Facebook, has listed a new app in stores as "Threads, an Instagram app", available for pre-order in the United States, with a message saying it is "expected" this Thursday.

The two men have clashed for years but a recent comment by a Meta executive suggesting that Twitter was not run "sanely" irked Musk, eventually leading to the two men offering each other out for a cage fight.