While some marked Independence Day with hot dogs and fireworks, anonymous hackers spent Monday morning breaking into a Fox News Twitter account and posting fake reports of a presidential assassination.

The prank tweets on the @foxnewspolitics account began just after 2 a.m., and — like any proper news account — kept updating with breathless posts on President Obama’s supposed condition.

The tweets, six in total, included gory (and entirely bogus) details: two shots at an Iowa restaurant, hitting the president in the pelvis and neck, etc.

Within hours, news of the fake assassination spurred a wave of re-tweets, jokes and comments mocking Fox online, fueled in part by idle Blackberrys during the holiday and, given the cruel nature of some tweets, apparently a measure of glee at the embarrassment of a news organization sometimes perceived as opposing Obama.

The Secret Service said it is launching an investigation, given the graphic and serious contents of the prank tweets. “We are investigating and will be conducting the appropriate follow-up,” said spokesman George Ogilvie.

Fox News apparently struggled for a few hours to regain control of its Twitter account. In the afternoon, it managed to remove the prank tweets and issued a statement on its Web site saying it “regrets any distress the false tweets may have created.”

Jeff Misenti, a company vice president and the general manager of Fox News Digital, also said in a statement that Fox News is requesting an investigation by Twitter.

In the @foxnewspolitics Twitter feed, an online outfit called the Script Kiddies initially took responsibility for the attack but then apparently deleted online information about itself, according to a student news Web site called Think at New York’s Stony Brook University.

Adam Peck, a writer for Think, relayed instant messages he exchanged with a person claiming to represent Script Kiddies in the wee hours of the morning right after the hack. One message said, “Fox News was selected because we figured their security would be just as much of a joke as their reporting.”