A US Army sergeant, on his third deployment in Iraq, has been charged the deaths of five other service people.

The sergeant killed the five by opening fire at the mental health clinic where he was being treated for combat stress.

Sgt John M. Russell, a communications specialist with the 54th Engineering Battalion, is in custody after the shooting at Camp Liberty on the outskirts of Baghdad.

He has been charged with five counts of murder and one of aggravated assault.

Camp Liberty is a heavily fortified complex near the airport that has essentially been sealed off from Iraqis to reduce threats to US soldiers.

According to military officials, Sergeant Russell had previously been deemed a threat to himself and others and was not allowed to have a weapon.

At the time of the shootings, Russell was going through a counseling process and was receiving other mental health assistance.

It is believed he had become involved in a fight at the clinic after which he returned with a stolen weapon.