Twitter suitor Musk tweets Elvis tune

In another tweet over the weekend, Musk, a self-described "free speech absolutist" who has been critical of Twitter and its policies, replied to a post of his from 2017 where he had asked "How much is it (Twitter)?" with an upside down smiley.

Musk, who is also the CEO of electric-vehicle maker Tesla, has amassed a 9.1 per cent stake in Twitter and is the social media firm's second-biggest shareholder.

Shares of Twitter rose 2.1 per cent to $US46.03 in pre-market trading on Monday, still significantly below Musk's offer of $US54.20 per share. The company's shares have risen roughly 15 per cent since Musk disclosed his stake on April 4.

Thoma Bravo, a technology-focused private equity firm that had more than $US103 billion ($A139 billion) in assets under management as of the end of December, informed Twitter that it was exploring the possibility of putting together a bid, people familiar with the matter told Reuters on Friday.