Online activists backing the regime of Syrian President Bashar al-Assad have claimed responsibility for hacking the Associated Press Twitter account.
A fake tweet which claimed President Obama had been injured in explosions at the White House led share prices on Wall Street to plunge.
The account has now been suspended and the FBI is investigating.
A group calling themselves the 'Syrian Electronic Army' has claimed responsibility.
They have previously successfully hacked the Twitter feeds of AFP and CBS News.
Here is a retweet of the offending fake tweet:
Breaking: Two Explosions in the White House and Barack Obama is injured via @AP
— Anonymous (@YourAnonNews) April 23, 2013