Elon Musk said on Friday his $44-billion deal for Twitter Inc was temporarily on hold, citing pending details on spam and fake accounts.

"Twitter deal temporarily on hold pending details supporting calculation that spam/fake accounts do indeed represent less than 5% of users," Musk said in a tweet.

Shares of the social media company fell 20% in premarket trading. Twitter did not immediately respond to a request for comment.

The company had earlier this month estimated that false or spam accounts represented fewer than 5% of its monetizable daily active users during the first quarter.

It also said it faced several risks until the deal with Musk is closed, including whether advertisers would continue to spend on Twitter.

Musk, the world's richest man and the chief executive of Tesla Inc, had said that one of his priorities would be to remove "spam bots" from the platform.