WASHINGTON – Billionaire Elon Musk said on Monday in a filing that he will be the chief executive officer of Twitter, the social media company he recently acquired for US$44 billion (S$62 billion).

The move comes after Mr Musk fired Twitter CEO Parag Agrawal and other top company officials last week.

Mr Musk also runs electric-vehicle maker Tesla, rocket company SpaceX, brain chip start-up Neuralink and tunnelling firm The Boring Company.

He previously changed his Twitter bio to “Chief Twit” in a sign alluding to this move.

Mr Musk’s takeover of Twitter last week concluded a months-long saga. Since then, he and a group of advisers have tightened their grip over Twitter.

They have met company executives to work on layoffs, ordered product changes, talked to advertisers and reviewed content moderation policies, according to more than a dozen current and former employees involved in the efforts.

The priorities for the world’s richest man and his advisers at Twitter are twofold, five of the people said: They are working on how to trim the company’s ranks, while also exploring a slew of changes to Twitter’s mobile app.

For now, the timing and scope of layoffs remain fluid as lists of the top and lower performers at the company are finalised, the people said.

Mr Musk’s advisers have also assigned a team of Twitter’s engineers to work on its “verification” program, the system that doles out badges to high-profile or notable users to confirm their profiles’ authenticity.

Twitter could charge users US$20 (S$28) a month to retain their verified status, two people with knowledge of the discussions said.

Mr Musk flew to New York on Sunday after spending much of last week at Twitter’s headquarters in San Francisco, according to one person familiar with his movements.

Some of his trusted confidants remain in San Francisco, the people said, including Mr David Sacks, a venture capitalist, and Mr Sriram Krishnan, a former Twitter product leader and partner at investment firm Andreessen Horowitz, which invested in the buyout of Twitter.

Other advisers, many of whom were in a “war room” with Mr Musk at Twitter’s headquarters last week, include Mr Jared Birchall, the head of Mr Musk’s family office; Mr Alex Spiro, his personal lawyer; and Mr Jason Calacanis, a tech investor and podcaster, said six people with knowledge of the matter.

Mr Musk also took about 50 engineers, product leaders and employees to Twitter from his other companies, according to four people with knowledge of the matter and internal documents viewed by The New York Times. NYTIMES, REUTERS