Islamic State group Cyber Caliphate hacked more than 54,000 Twitter accounts and leaked credentials Nov. 8 in retaliation for an August drone attack that killed one of its members, according to The Daily Express.

The group tweeted, "We need years to publish what we have. We will raise our flag in the heart of Europe," before tweeting a link to the database of stolen credentials from a Twitter account that has since been suspended.  

The compromised accounts were reportedly used to spread ISIS propaganda after ISIS member Junaid Hussain, a British citizen that steered the group's hacking division, was killed.

Most accounts belonged to victims in Saudi Arabia but some may have been British citizens, the report said.

The group also posted personal details including cell phone numbers of the heads of the Central Intelligence Agency (CIA), Federal Bureau of Investigation (FBI) and National Security Agency (NSA).