The Twitter feed for Fox News' political news -- @FoxNewspolitics -- sent out a series of "malicious and false tweets," starting around 2:00 am, Fox News confirmed in a statement. The posts had not been taken down hours later.

"@BarackObama has just passed. The President is dead. A sad 4th of July, indeed. President Barack Obama is dead," read the first of the Obama-related tweets. Just before false posts began, the hackers apparently announced their control to the account, with the post: "Just regained full access to our Twitter and email. Happy 4th."

The updates, which were "retweeted" by thousands on the micro-blogging site and prompted headlines around the world, said Obama had been "shot twice at a Ross' restaurant in Iowa" during a campaign spot.

The US leader is in fact in Washington, not Iowa, and was planning to celebrate the July 4 holiday with his family and military families later Monday.

"President @BarackObama assassinated, 2 gunshot wounds have proved too much. It's a sad 4th for #america. #obamadead RIP," continued the tweets.

Fox News said the hacking was being investigated, and that it "regrets any distress the false tweets may have created."

Copyright AFP (Agence France-Presse), 2011