A regulatory filing shows that Elon Musk has fired Twitter's board of directors and made himself the firm's chief executive officer.

The filing by the US Securities and Exchange Commission says Musk had taken control as of Thursday when he completed his acquisition of the social media company.

All nine directors were fired, including former CEO Parag Agrawal. This makes Musk the board's sole member.

He tweeted that the move was "just temporary," but he did not elaborate.

It's believed the mass firing was aimed at speeding up the firm's decision-making process and accelerate reforms. But the move has also led to a concentration of power by Musk.

After completion of the purchase, Musk said he would set up a council to monitor and delete inappropriate tweets.

But he recently tweeted a link to a baseless article about an assault on the husband of US House Speaker Nancy Pelosi.

That tweet has come under fire and raised questions on the control of tweet content.