Newsweek magazine's Twitter account was the victim of hackers who posted a threat to US President Barack Obama and his family and the words "CyberCaliphate" and "Je suis IS," a reference to Islamic State and the French magazine Charlie Hebdo.
The group, which also took responsibility for hacking Pentagon social media accounts last month, tweeted "#CyberCaliphate Bloody Valentine's Day #MichelleObama! We're watching you, you girls and your husband!"
It also posted a message intended for the United States in retaliation for its actions in the Muslim world.
"While the US and its satellites are killing our brothers in Syria, Iraq and Afghanistan, we are destroying your national cybersecurity system from inside," it said.
The message contained a list of names under the heading "brave mujahideen."
Newsweek removed the CyberCaliphate banner and tweets by mid-morning. It was not immediately clear how long the intrusion lasted.
The group took responsibility for the intrusion last month of the Twitter and YouTube accounts for the US Central Command, which oversees operations in the Middle East. The hackers claimed to be sympathetic toward the Islamic State militant group being targeted in American bombing raids.
