Islamic State-inspired terror attacks might be carried out against United States law enforcement, including police officers and government workers, as well as "media figures" across the country, federal officials warned.

Increasing calls for violence on social media forums and a recorded audio message urging lone offenders in Western countries to attack "soldiers, patrons, and troops ... their police, security and intelligence members" was cited by the FBI and Department of Homeland Security in a joint intelligence bulletin sent to U.S. law enforcement officials and confirmed by Fox News.

In one instance, ISIS spokesman Abu Muhammad al-Adnani's English-translated message was posted on a jihadi forum in late September, asking attackers to refrain from taking anyone's advice before striking because such actions are legitimate, according to NBC News.

Another document posted by an ISIS supporter in September reportedly advocated "open source jihad" and "lone wolf operations" by U.S. Muslims against "a list of potential targets, including military, law enforcement, FBI personnel, government officials and media figures."

"I requested it as a duty to warn and as an officer safety matter given ISIL's continued statements on forums and in social media to conduct homeland attacks and to target law enforcement, government and intelligence agencies," a senior intelligence official told Fox News, adding that "FBI investigator" was specifically mentioned in one post.

"Once a terror organization urges such action -- regardless of whether any adherents might take action -- terrorism officials need to get the word out to increase state and local officials', as well as reporters', awareness. In the case of ISIS, given their skilled use of social media, these threats to inspire 'lone wolves' produce a bit more urgency for intelligence and law enforcement officials."

Citing recent arrests overseas, the senior intelligence official told Fox News that "the fact media has reported arrests in the UK and Australia based on plots to target police and lastly given the stabbing of an AFP [Australian Federal Police] officer, we felt it important to get the information out to all law enforcement." 

Meanwhile, even though the credibility of the threat by homegrown extremists was not confirmed, taking "additional precautions" when conducting interviews would prove helpful for law enforcement and FBI personnel, the bulletin advised.