The Defense Department on Friday asked armed civilians who have volunteered to guard military recruiting stations across the country in the wake of the mass shooting in Chattanooga, Tenn., to leave their posts.

The Pentagon said in a statement that it took the safety of its enlisted and civilian personnel “very seriously” and that Defense Secretary Ashton B. Carter was reviewing recommendations to improve security at all facilities, including recruiting stations.

The presence of armed civilians, it said, might cause safety problems.

“While we greatly appreciate the outpouring of support for our recruiters from the American public, we ask that individuals not stand guard at recruiting offices as it could adversely impact our mission, and potentially create unintended security risks,” Peter Cook, the Pentagon press secretary, said. “We continue to partner with and rely on first responders for the safety of the communities where our service members live and work.”

Civilians — often heavily armed, sometimes dressed in camouflage combat fatigues, and overwhelmingly male — have volunteered to stand guard outside recruiting centers since the shooting July 16 at a military reserve center and a nearby recruiting center in Chattanooga. Among those killed were four United States Marines, a member of the Navy and the gunman, Mohammod Abdulazeez. Two people were wounded.