Staff Sgt. Glen Brott, 90th Security Forces Group Tactical Response Force assaulter, moves toward a breached personnel access hatch during a launch facility re-capture exercise at F.E. Warren Air Force Base, Wyo., Feb. 18, 2014. (U.S. Air Force photo by Staff Sgt. Jonathan Snyder/RELEASED)

The U.S. military has boosted security at all of its stateside bases and stations, broad recognition that the United States has heightened its awareness of a possible attack inspired by the Islamic State militant group, U.S. officials said Friday.

The force protection condition was upped from “Alpha” to “Bravo,” the middle of five steps on the military’s scale, said Army Col. Steve Warren, a Pentagon spokesman. It means that the military believes there is an increased and predictable security threat at home, with extra precautions, ID checks and searches launched across the country. It does not mean that an attack is considered imminent, however.

The decision, first reported by CNN, was made by U.S. Northern Command, which oversees homeland security for the Defense Department. and comes at a time when militants in Iraq, Syria and other countries in the Middle East and Africa have called for attacks on U.S. troops at home and abroad.

[Pentagon security agency: Watch out for Islamic State attacks in the U.S.]

FBI Director James Comey told reporters Thursday that investigators are pursuing hundreds of investigations related to the Islamic State in the United States. On Sunday, gunmen believed to be inspired by the Islamic State group also opened fire on police guarding a civilian gathering in Garland, Tex., where a contest was underway to draw the prophet Muhammad.

“We have a general concern, obviously, that ISIL is focusing on the uniformed military and law enforcement,” Comey said, using one of the acronyms for the militant group.

[One Texas suspect was accused in 2010 FBI terror case]

Warren declined to pinpoint why security was elevated, but noted that the Defense Department has been tracking a variety of social media accounts that send threatening messages.

“This is not in response to any specific, identifiable threat stream,” Warren said. “There is no threat to a specific place. What this is a generally heightened threat environment.”

The force protection level was last at Bravo in 2011, around the 10th anniversary of the terrorist attacks on Sept. 11, 2001, Warren said. At some bases recently, some of the measures from condition Bravo already were in place, he added.

The next threat level, “Charlie,” indicates that an incident has occurred or intelligence has been gathered showing that an attack is imminent. The highest level, “Delta,” is designated for when the military has intelligence indicating an attack on a specific facility is imminent, or has already occurred.

Adam Goldman contributed to this report.