Twitter is investigating after the social media network’s co-founder and chief executive Jack Dorsey had his account hacked.
A series of offensive and racist messages were posted to Dorsey 4.2m followers on Friday evening.
Among them included false reports of a bomb threat at Twitter’s headquarters and messages defending Adolf Hitler.
It took around 30 minutes for them to be taken down.
A Twitter statement said: “We’re aware that @jack was compromised and [are] investigating what happened.
It added later: “The account is now secure, and there is no indication that Twitter’s systems have been compromised.”
Some of the messages referred to “The Chuckling Squad”, the alleged name of the group behind the hack.
Following the incident some Twitter users have questioned how the platform’s own boss could have his account hacked.
For some it has raised concerns of what could happen if people in positions of power, such as US President Donald Trump, have their accounts hacked.
It comes as Twitter pledged to crack down on abusive and racist messages, often sent from anonymous accounts.
In July the Metropolitan Police lost control of their Twitter account when a series of bizarre messages were shared.
Words like “Chuckling” and “Hella” featured in messages posted in both hacks.
Twitter’s shares fell by just under one per cent in after-hours trade in the wake of the incident.