US military prosecutors said they would seek the death penalty for a soldier accused of killing 16 Afghan villagers on two drunken forays earlier this year. Lead prosecutor Lieutenant Colonel Jay Morse told a preliminary hearing on Monday he would present evidence proving "chilling premeditation" on the part of Staff Sergeant Robert Bales, a 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 slaughter blamed on an individual US soldier since the Vietnam War. It also eroded already strained US-Afghan ties after more than a decade of conflict in the country. Bales faces 16 counts of premeditated murder and six counts of attempted murder, as well as charges of assault and wrongfully possessing and using steroids and alcohol while deployed. Morse said he was submitting a "capital referral" in the case, requesting that Bales be executed if convicted. The hearing at Joint Base Lewis-McChord in Washington state is expected to last two weeks and include testimony carried by live video from witnesses in Afghanistan, including villagers and Afghan soldiers. At the end, military commanders will decide whether there is sufficient evidence for Bales to stand trial by court martial. Bales, dressed in camouflage Army fatigues and 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 Morse summarised the prosecution's account of the events of March 10-11. According to Morse, 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. Morse said Bales then returned to the camp and told one of his drinking buddies, Sergeant Jason McLaughlin, "I just shot up some people," before leaving again for a second village and killing more people. Morse called Bales' actions "deliberate, methodical." The prosecution showed a video shot by night-vision camera from a surveillance balloon over the camp, showing a figure they identified as Bales walking back to the post wearing a dark blue bed sheet tied around his neck like a cloak. He is seen being confronted by three soldiers, including the two men that prosecutors said he had been drinking with, who ordered him to drop his weapons. They then take him into custody as he is heard saying: "Are you kidding me?" One of the three, Corporal David Godwin, testified that Bales kept repeating the words, "I thought I was doing the right thing," and "It's bad. It's bad. It's really bad." Prosecutors said Bales had been armed with a rifle, a pistol and a grenade launcher. They said the killings took place over a five-hour period in two villages and the dead included members of four families. Most were shot in the head. John Henry Browne, Bales' civilian lawyer, has suggested that Bales may not have acted alone and could be suffering from post-traumatic stress disorder.