"It appears as though AP's Twitter account has been attacked, so anything that was just sent out is false," Julie Pace, AP's White House correspondent, said at the daily briefing by White House press secretary Jay Carney.
Carney added the president was fine.
Other AP accounts, including its breaking news and Stylebook feeds, were not affected by the attack, CBS News said. The Twitter account has been temporarily suspended.
The bogus news, which came shortly after 1 p.m. Tuesday, caused Wall Street's Dow Jones Industrial Average to drop 145 points in minutes, but it recovered within a half hour, The Wall Street Journal reported.
Hackers who support Syrian President Bashar Assad claimed responsibility Tuesday for hijacking the account, the Los Angeles Times reported.
"Ops! @AP get owned by Syrian Electronic Army! #SEA #Syria #ByeByeObama" an account tied to the hacking group tweeted, linking to a screenshot of the hacked AP account.
The group had previously claimed to have hacked Twitter accounts for CBS, the International Federation of Association Football and the BBC.