Billionaires Elon Musk, Jeff Bezos and Bill Gates are among many prominent US figures targeted by hackers on Twitter in an apparent Bitcoin scam.
The official accounts of Barack Obama, Joe Biden and Kanye West also requested donations in the cryptocurrency.
"Everyone is asking me to give back," a tweet from Mr Gates' account said. "You send $1,000, I send you back $2,000."
Twitter said it was a "co-ordinated" attack targeting its employees "with access to internal systems and tools"
"We know they [the hackers] used this access to take control of many highly-visible (including verified) accounts and Tweet on their behalf," the company said in a series of tweets.
It added that "significant steps" were taken to limit access to such internal systems and tools while the company's investigation was ongoing.
Meanwhile, Twitter CEO Jack Dorsey tweeted: "Tough day for us at Twitter. We all feel terrible this happened."
As well as rapper Kanye West, his wife, reality TV star Kim Kardashian, former US President Obama, Mr Biden, who is the current Democratic presidential candidate, and media billionaire Mike Bloomberg, major companies Uber and Apple were targeted.
The Biden campaign said Twitter had "locked down the account within a few minutes of the breach and removed the related tweet".
A spokesman for Bill Gates told AP news agency: "This appears to be part of a larger issue that Twitter is facing."