The Syrian Electronic Army, the cyber-wing of Syrian president Bashar al-Assad's regime, has targeted Barcelona football club because of its ties to Qatari money which is "full of blood and kill."
Three accounts - @FCBarcelona, @FCBarcelona_es and @FCBarcelona_cat - each of which has millions of followers, were compromised by the SEA on Wednesday morning, following Barcelona's 2-0 defeat of Manchester City in the Champion's League on Tuesday night.
The hackers posted the same message on all three accounts, saying:
"Dear FC Barcelona management, don't let the Qatari money funds you, it's full of blood and kill."
For many years Barcelona refused corporate sponsorship on the front of their shirt but prior to the start of the 2011–12 season the club signed a five-year €150 million (£123m) deal with Qatar Sports Investments.
The deal saw the logo of the Qatar Foundation featured on the club's shirt for the 2011/12 and 2012/13 seasons, replaced by Qatar Airways for the beginning of the current season, with the deal allowing for a commercial sponsor logo to replace the charity logo, two years into the five-year deal.
The offending tweets have now been removed, with Barcelona saying: "This twitter account has been used fraudulently. The improper tweets have been removed. We apologise for any inconvenience."
The SEA has subsequently claimed that it was Twitter who removed the tweets the group posted and not Barcelona's social media team. IBTimes UK has asked Twitter to confirm this but at the time of publication have not received a reply.
The breach of Barcelona's Twitter accounts comes a week after the group hacked into the Forbes.com system, defacing the Forbes websites, compromising several Twitter accounts and stealing emails and passwords for over 1 million user accounts.
Details of how the accounts were hacked have not been revealed, but in previous attacks on high-profile media organisations like Sky, the Guardian and the BBC, the attacks have been carried out using targeted phishing emails, sent to employees and containing links to malicious sites which tricked them into revealing login credentials.