Last month, the pair agreed to a physical fight, though it is unclear how serious the two men were about actually holding a bout.

“Thank goodness they’re so sanely run”, Mr Musk responded to a tweet about Threads, in an apparent fresh swipe at Mr Zuckerberg.

The move is the latest push by Mr Musk as he tries to get users to sign up to Twitter’s subscription service, Twitter Blue.

On Saturday, the multi-billionaire restricted the number of tweets users could see, citing extreme “data scraping”.

It appears from Meta’s Threads app that it will be a free service – and there will be no restrictions on how many posts a user can see.

“Threads is where communities come together to discuss everything from the topics you care about today to what’ll be trending tomorrow” the description on the App Store says.

Pictures show screengrabs from the app, that look almost identical to Twitter.

Several apps that bear a striking resemblance to Twitter have sprung up in recent years – such as Donald Trump’s Truth Social and Mastodon.

Another similar app, Bluesky claimed to have seen “record” traffic after Mr Musk’s move to restrict usage at the weekend.

However, Threads could be the biggest threat faced by Twitter to date.

Mark Zuckerberg has a history of borrowing other company’s ideas – and making them work.

Meta’s Reels is widely seen as a TikTok copy, while Stories looks similar to Snapchat.

Although Mr Musk has been praised in some quarters for his commitment to free speech, he has also alienated some users.

Mr Zuckerberg will hope he can pull enough disenchanted users away from Twitter to create a genuine alternative.