WASHINGTON -- The Army has warned its recruiters to treat the gun-toting civilians gathering at centers across the country in the wake of the Chattanooga, Tenn., shooting as a security threat.

Soldiers should avoid anyone standing outside the recruiting centers attempting to offer protection and report them to local law enforcement and the command if they feel threatened, according to a U.S. Army Recruiting Command policy letter issued Monday.

Armed citizens -- some associated with activist groups and militias -- were standing vigil outside recruiting centers in Wisconsin, Georgia, Tennessee, Idaho and elsewhere this week, saying they want to provide protection to servicemembers barred from carrying firearms on duty. Four Marines and a sailor were killed by Mohammad Youssef Abdulazeez, a 24-year-old Kuwait-born native of Tennessee, during an attack Thursday on a strip mall recruiting center and a Navy facility that is being investigated as an act of terrorism.

Abdulazeez fired into the front of the recruiting station but there were no casualties. The five servicemembers were killed during an attack on the Navy Operational Support Center. A Navy officer and a Marine reportedly fired at the gunman, although it is unclear why they were armed. It is against Defense Department policy for anyone other than military police or law enforcement to carry weapons on federal property.

"I'm sure the citizens mean well, but we cannot assume this in every case and we do not want to advocate this behavior," according to the Army Command Operations Center-Security Division letter, which was authenticated by the service.

Recruiters were ordered not to interact or acknowledge the armed civilians, who have been greeted by a mix of concern, indifference and gratitude by the public.

"If questioned by these alleged concerned citizens, be polite, professional and terminate the conversation immediately and report the incident to local law enforcement …," the command advised.

As the incidents crop up around the country, police could be asked to confront the civilians with guns on the Army's behalf.

"Ensure your recruiters clearly articulate to local police the civilian may be armed and in possession of a conceal/carry permit," it told the centers.

The command said recruiters should also immediately fill out an Army security report.

Kelli Bland, a spokeswoman for Army Recruiting Command, said the service has been increasing vigilance following the Chattanooga shooting and that local residents can help in other ways.

"Local communities can support our security by reporting suspicious activity, particularly around recruiting centers," Bland wrote in an email to Stars and Stripes.

Concerned citizens began gathering at the centers shortly after the shooting in Tennessee, and governors in some states ordered recruiters to armories or to be armed for protection against potential terrorist attacks. Congress has also pushed for the Defense Department to lift its current policy.

The founder and president of Oath Keepers, a Constitution activist group based in Las Vegas, issued a national call Tuesday to guard centers, while members were already guarding centers in Tennessee, Arkansas and Oklahoma, president Stewart Rhodes told the Associated Press.

Rhodes told the news service it's "absolutely insane" that recruiters aren't allowed to be armed.

"They're sitting ducks," Rhodes said Tuesday. "They'd be better off if they were walking down the streets of Baghdad, because at least in Baghdad, they could move. Here, they're stationary."

In Lewiston, Idaho, three men with a group known as "3 percenters" -- a national alliance with members who prepare "for any situation, man-made or natural" -- were standing watch outside a recruiting office this week, the TNS wire service reported.

"They supported us, and now we're here showing them that we support them," said Matt Dillard, of Clarkston, Idaho, who was among the men.