The Pentagon has softened rules on US troops carrying firearms while at government facilities, an action prompted by a series of deadly attacks on uniformed personnel.

Troops already carry weapons as part of certain job functions, but the new rules will allow commanders to authorize the carrying of privately owned handguns, according to a November 18 directive.

Commanders may grant permission to Department of Defense "personnel requesting to carry a privately owned firearm (concealed or open carry) on DoD property for a personal protection purpose not related to performance of an official duty or status," the directive states.

In July last year, an attack on a Chattanooga, Tennessee recruitment center and a Navy and Marine Corps reserve center left four marines and one sailor dead at the hands of a lone gunman, who according to the FBI was inspired by radical Islamist propaganda.

The rampage prompted Congress to ask President Barack Obama's administration to loosen current regulations on US troops carrying arms.

On November 5, 2009, Major Nidal Hasan, 39, a US Army psychiatrist of Palestinian origin opened fire with a pistol at the Fort Hood base in Texas, killing 13 people and wounding more than 40 before he was arrested.

The new policy has no bearing on firearms regulations for US troops in war zones.