The Twitter account and YouTube page for U.S. Central Command were hacked on Monday and for several minutes carried incendiary messages promoting the Islamic State -- including one that said, "AMERICAN SOLDIERS, WE ARE COMING, WATCH YOUR BACK. ISIS."
The cyber-attack sent U.S. military officials scrambling to respond, and they temporarily suspended both accounts.
Late Monday, Central Command's Twitter account was back online, with a message proclaiming, "We're back! CENTCOM temporarily suspended its Twitter account after an act of cybervandalism." The YouTube channel remained offline as of Tuesday morning.
President Obama briefly addressed the incident at the White House on Tuesday. He said the Twitter account was hacked by "Islamist Jihadist sympathizers," and it "goes to show how much more work we need to do" on cybersecurity. He said he plans to talk about cybersecurity in his upcoming State of the Union address.
Officials said they're still investigating the hack, but claimed it appears no classified information was released.
"We're still looking into this," Central Command spokesman Col. Patrick S. Ryder said. "Our initial assessment is that no classified information was posted."
A statement from Central Command added that their operational military networks "were not compromised" and downplayed the incident as "a case of cybervandalism."
Still, the tweets contained what appeared to be military plans and contact information for military officials -- one posting even showed what appeared to be an image from a computer web cam in a military facility.
An accompanying tweet said, "ISIS is already here, we are in your PCs, in each military base."
Officials have not explained how the hackers got that information, or the web cam image. Central Command said in a statement that "none of the information posted came from CENTCOM's server or social media sites," and that they are "notifying appropriate DoD and law enforcement authorities about the potential release of personally identifiable information and will take appropriate steps to ensure any individuals potentially affected are notified as quickly as possible."
The Twitter account, while it was compromised, carried an image identifying the page as "CyberCaliphate," with a message that said, "I love you ISIS."
The hacker group may be the same one that is under FBI investigation for hijacking the websites or Twitter feeds of media outlets in the last month, including a Maryland television station and a New Mexico newspaper.
The intrusion on the military Twitter account carried the same logo, CyberCaliphate name and photo that appeared on the Albuquerque Journal's website in late December when one of its stories was hacked. And earlier this month, it appeared that the same hackers breached the Journal's Twitter account and also took over the website and Twitter feed of WBOC-TV in Salisbury, Maryland.
The FBI at the time acknowledged it was looking into the Albuquerque case, and WBOC said it was also in contact with the agency.
The monitoring group MEMRI said the CyberCaliphate group began operating "only recently," noting the group also claimed to have hacked the FBI's New Mexico office earlier this month.
Asked about the hack on Monday, White House Press Secretary Josh Earnest said it's "something we take very seriously." But he stressed there is a difference between a "large data breach" and the "hacking of a Twitter account." He said officials are investigating the extent of the incident.
The Twitter page, after the breach, began posting screen shots of information about military commanders, including phone numbers and email addresses. It also posted what purported to be "Korean scenarios" and "China scenarios," with maps.
The same "CyberCaliphate" image at the top of the hacked Twitter page was briefly emblazoned atop Central Command's YouTube page.
"This is bad," one Central Command source told Fox News as the messages were still being posted.
Shortly after the Twitter account was taken over, the account was suspended, as was the YouTube page. A message on the YouTube page says the account "has been terminated due to repeated or severe violations of our Community Guidelines."
A Defense official earlier told Fox News that the Twitter account was "compromised," and that "CENTCOM is taking appropriate [measures] to address the matter."
Fox News' Jennifer Griffin and Catherine Herridge and The Associated Press contributed to this report.