The tweets remained on the website hours after they were posted. Twitter

The U.S. Secret Service will investigate the hijacking of a Fox News Twitter account by hackers who posted false reports that U.S. President Barack Obama was assassinated.

Secret Service spokesman George Ogilvie confirmed the investigation to CBC News on Monday.

Six tweets from FoxNewsPolitics, which has more than 34,100 followers, alleged the president was shot and killed at a restaurant while campaigning in Iowa. They were posted starting at about 2 a.m. ET on Monday, Independence Day.

Fox News announced on its website later in the morning that it had alerted the Secret Service, which is responsible for protecting the president, about the incident.

On its website Monday morning, FoxNews.com said, "Hackers sent out several malicious and false tweets claiming that President Obama had been assassinated.

"Those reports are incorrect, of course, and the president is spending the July 4 holiday with his family."

Fox News, which is based in New York City, later added it had alerted the Secret Service. Jeff Misenti, vice-president and general manager of Fox News Digital, was quoted as saying the website was requesting a detailed investigation by Twitter to figure out how the attack occurred and how to "prevent future unauthorized access into FoxNews.com accounts."

FoxNews.com expressed regrets for "any distress the false tweets may have created."

A group called the Script Kiddies initially took responsibility for the attack but later deleted information about itself from the Twitter feed, reported Think, a student news website at New York's Stony Brook University, which followed the attack as it progressed.

A person claiming to be from the Script Kiddies told the website the group includes former members of Anonymous, a loose-knit group of hackers who had taken responsibility for cyber attacks on various governments, including Tunisia and Egypt, as well as businesses that include MasterCard and Visa.

The spokesperson said the Script Kiddies are involved in an activist "antisec" movement targeting computer security that both Anonymous and Lulz Security are part of.

"Fox News was selected because we figured their security would be just as much of a joke as their reporting,” the group told the magazine. As of Monday morning, its apparent Twitter accounts, @TheScriptKiddie and @scriptkiddi3s, were suspended.

A purported Script Kiddies spokesperson gave similar information to TheHackerNews.com. He or she also claimed the group had access to several Fox News email accounts.

Tweets from the hacking incident remained online until around noon ET, including: "BREAKING NEWS: President @BarackObama assassinated, 2 gunshot wounds have proved too much. It's a sad 4th for #america. #obamadead RIP," and "We wish @joebiden the best of luck as our new President of the United States. In such a time of madness, there's light at the end of tunnel."

Security blogger Graham Cluley wrote that "may mean that no one at Fox has been able to log into the account to remove the tweets."

Cluley, a senior technology consultant for the computer security firm Sophos, noted that the rogue tweets started just after a post on the FoxNewsPolitics Twitter account saying, "Just regained full access to our Twitter and email. Happy 4th."

He suggested this means someone gained access to the Twitter account by compromising the email address of the person who administers it.

As of 9:30 a.m. ET Monday, Twitter had not commented on the attack, and its media inquiries website returned an error message with the suggestion to "Try again later."

On Monday, the only tweet issued by Twitter's official account was one asking the public to tweet questions for President Barack Obama for an online White House town hall on Wednesday.

With files from The Associated Press