The US soldier who allegedly shot 16 Afghan villagers was caught on surveillance video that showed him walking up to his base, laying down his weapon and raising his arms in surrender, according to an Afghan official who viewed the footage.

The official said late on Tuesday that US authorities showed Afghan authorities the surveillance video to prove that only one perpetrator was involved in the Sunday shootings, which have further strained already shaky relations between the US and Afghanistan.

Any major discrepancy between the official Afghan and US accounts of the killing is likely to deepen the distrust.

One member of an Afghan government delegation investigating the killings said on Wednesday that the group has concluded the shooting spree was carried out by more than one soldier. Parliament member Sayeed Ishaq Gilani said the delegation had heard from villagers who said they saw more than 15 troops at the scene.

But it's unclear whether the soldiers the villagers saw were part of a search party that left the base to look for the US soldier who was missing. The delegation is slated to formally release the results of its investigation later today.

On Tuesday, the delegation visited the two villages in Kandahar province where the shootings took place. Two villagers who lost relatives insisted that at least two soldiers took part in the shootings.

US military officials continue to believe that only one soldier was involved.

"We are still receiving, reviewing and investigating all leads in connection with this terrible incident, but at this time everything still points to one shooter," said Lieutenant Colonel Jimmie Cummings, a spokesman for the US-led coalition.

The surveillance video, taken from an overhead blimp that films the area around the base, shows a soldier in a US uniform approaching the south gate of the base with a traditional Afghan shawl hiding the weapon in his hand, the Afghan official said.

He then removes the shawl as he lays his weapon on the ground and raises his arms in surrender.

The official had not been shown any footage of the soldier leaving the base. The official spoke anonymously to discuss a private briefing.

The Taliban has vowed revenge for the shootings.

Afghan lawmakers have demanded that the alleged shooter, identified by US officials as a staff sergeant, face a public trial inside Afghanistan. They have called on Afghan President Hamid Karzai to suspend any negotiations with the US on a long-term military pact until this happens. "No final decision has been made yet" on the location of the trial, said Colonel Gary Kolb, a US military spokesman in Afghanistan.

Kolb said that the US has held courts-martial in Afghanistan before, and could try the alleged shooter in the country. "They'll take a look at all the circumstances and determine if they do it here or if it goes back to the States."

The US is holding the soldier, who military officials say slipped off a US base before dawn on Sunday, walked to the villages, barged into their homes and opened fire. Some of the corpses were burned. Eleven were from one family. Five other people were wounded.

The military said Tuesday there was probable cause to continue holding the soldier, who has not been named, in custody. US Secretary of Defense Leon Panetta has said he could face capital punishment.

Panetta arrived in Afghanistan on Wednesday on a visit that was planned months before the weekend slaughter of Afghan villagers. But the trip propels Panetta into the center of escalating anti-American anger and sets the stage for some difficult discussions with Afghan leaders.

Panetta and other US officials say the shooting spree should not derail the US and NATO strategy of a gradual withdrawal of troops by the end of 2014.

But it has further soured relations with war-weary Afghans, jeopardizing the US strategy of working closely with Afghan forces so they can take over their country's security.

Afghan Defense Minister Abdul Rahim Wardak called the massacre "deplorable" on Wednesday but said the country must remember the bigger issues at stake, likely a reference to the fear that the Taliban could capitalize on a precipitous foreign withdrawal.

"I mean the stakes are much higher than this incident, which we have all have condemned, and I think we are assured that the US authority will take appropriate action," said Wardak in a press conference with German Defense Minister Thomas de Maiziere in Kabul.

Associated Press