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.
Meanwhile, Twitter CEO Jack Dorsey tweeted: "Tough day for us at Twitter. We all feel terrible this happened."
On the official account of Mr Musk, the Tesla and SpaceX chief appeared to offer to double any Bitcoin payment sent to the address of his digital wallet "for the next 30 minutes".
"I'm feeling generous because of Covid-19," the tweet added, along with a Bitcoin link address.
The tweets were deleted just minutes after they were first posted.
But as such tweet from Musk's account was removed, another one appeared, then a third.
Others targeted included:
- the rapper Kanye West
- his wife, reality TV star Kim Kardashian
- former US President Obama
- former US Vice-President Joe Biden, who is the current Democratic presidential candidate
- media billionaire Mike Bloomberg
- the ride-sharing app Uber
- the iPhone-maker Apple
The BBC can report from a security source that a web address - cryptoforhealth.com - to which some hacked tweets directed users was registered by a cyber-attacker using the email address mkeyworth5@gmail.com.
The name "Anthony Elias" was used to register the website.
Cryptoforhealth is also a registered user name on Instagram, apparently set up contemporaneously to the hack.
The Instagram profile also posted a message that said: "It was a charity attack. Your money will find its way to the right place."
