Hackers calling themselves "CyberCaliphate" threatened U.S. President Barack Obama and his family when they took control of Newsweek magazine's Twitter account on Tuesday with the words "Je suIS IS," a reference to Islamic State and the deadly attack at French newspaper 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!"

The FBI is investigating the hacking, White House spokesman Josh Earnest said. He did not comment specifically on the threat to the first family. The FBI had no immediate comment.