US military prosecutors have said they will seek the death penalty for a soldier accused of killing 16 Afghan villagers.

Staff Sergeant Robert Bales is alleged to have carried out the killings when he ventured out of his camp on two revenge-fuelled drunken forays earlier this year.

Lead prosecutor US Lieutenant Colonel Jay Morse told a preliminary hearing he would present evidence proving "chilling premeditation" on the part of Sgt Bales.

The soldier is a decorated veteran of four combat tours in Iraq and Afghanistan.

The shootings of mostly women and children in Afghanistan's Kandahar province in March marked the worst case of civilian deaths blamed on an individual US soldier since the Vietnam War.

Sgt Bales faces 16 counts of premeditated murder and six counts of attempted murder.

He also faces charges of assault and wrongfully possessing and using steroids and alcohol while deployed.

Lt Col Morse said he was submitting a "capital referral" in the case, requesting that Sgt Bales be executed if convicted.

The hearing at Joint Base Lewis-McChord in Washington state is expected to last two weeks.

It will include witness testimony from Afghanistan carried by live video, including testimony from villagers and Afghan soldiers.

At the end, military commanders will decide whether there is sufficient evidence for Sgt Bales to stand trial by court martial.

Sgt Bales, dressed in camouflage army fatigues with his head shaven, embraced his wife in court before the hearing began.

He then sat silently watching the proceedings from the defence table as Lt Col Morse summarised the prosecution's account of the events of 10-11 March.

The court heard that Sgt Bales had been drinking with two fellow soldiers before he left his base, Camp Belambay, and went to a village where he committed the first killings.

Sgt Bales then returned to the camp and told a drinking buddy, Sergeant Jason McLaughlin: "I just shot up some people," before leaving for a second village and killing more people.

Prosecutors showed a video shot by night-vision camera from a surveillance balloon over the camp, showing a figure they identified as Sgt Bales walking back to the post wearing a dark blue bed sheet or throw rug tied around his neck like a cloak.

Several witnesses from the camp said Sgt Bales had been aggrieved over the lack of action over an improvised explosive device attack on a patrol near the camp several days earlier, in which one US soldier lost the lower part of a leg.

Prosecutors said Sgt Bales had been armed with a rifle, a pistol and a grenade launcher on the night in question, and that the killings took place over a five-hour period in two villages.

The dead included members of four families, most shot in the head.

John Henry Browne, Sgt Bales' civilian lawyer, has suggested the accused may not have acted alone and may be suffering from post-traumatic stress disorder.

The shootings highlighted discipline problems among US soldiers from Lewis-McChord, which was also the home base of four enlisted men from the former 5th Stryker Brigade who were convicted or pleaded guilty to murder or manslaughter over three killings of unarmed Afghan civilians in 2010.