A joint intelligence bulletin sent to law enforcement agencies by the FBI and the Department of Homeland Security urged members of the US military to erase from their online social media accounts anything would draw attention from "violent extremists," or reveal service members' identity, the news network said.
ABC said the government indicated late Sunday it had obtained intelligence that ISIL militants, who have taken over parts of Iraq and Syria with the intention of setting up a fundamentalist caliphate, were targeting the United States within its borders.
"The FBI recently received reporting indicating individuals overseas are spotting and assessing like-minded individuals who are willing and capable of conducting attacks against current and former US-based members of the United States military," the bulletin said.
An FBI spokesman confirmed the accuracy of the ABC report, but declined to provide a copy of the memo, Reuters reported.
US Army Colonel Steve Warren, a Pentagon spokesman, said the advisory "reinforces the guidance that our combatant commanders had put out several weeks ago."
The Pentagon had most recently advised personnel to check their social media after two Canadian soldiers were killed in their country in October in separate attacks, he said.
"The department has long been aware and mindful of the potential for homegrown extremism and we have continued to encourage and to advise all of our personnel to exercise the maximum amount of vigilance," Warren said.
A US government source told Reuters the warning most likely was issued in response to an upsurge in social media postings by suspected militants threatening US service members.