Elon Musk has taken a 9.2 per cent stake in Twitter, according to a US securities filing.

The news sent Twitter shares soaring about 25 per cent in pre-market trading.

The Tesla founder bought 73,486,938 Twitter shares on March 14, according to the Securities and Exchange Commission.

The stake is worth $2.89billion (£2.20billion), based on Twitter's closing price on Friday.

Musk is a regular Twitter user with more than 80 million followers, although recently he said he is giving "serious thought" to building a new social media platform.

Late last month Musk asked his followers whether they thought the social medial platform encouraged free speech.

"Free speech is essential to a functioning democracy. Do you believe Twitter rigorously adheres to this principle?"

He then asked: "Is a new platform needed?"