The American soldier accused of shooting 16 Afghan villagers in a pre-dawn killing spree was flown out of Afghanistan on Wednesday to Kuwait, even as many Afghans called for him to face justice in their country.

Afghan government officials did not immediately respond to calls for comment on the late-night announcement. The U.S. military said the transfer did not preclude the possibility of trying the case in Afghanistan, and Defense Secretary Leon Panetta has said the soldier could receive capital punishment if convicted.

The soldier was held by the U.S. military in Kandahar until Wednesday evening, when he was flown out of Afghanistan to Kuwait, said a U.S. official who spoke on condition of anonymity because of the sensitivity of the matter.

Many fear a misstep by the U.S. military in handling the case could ignite a firestorm in Afghanistan that would shatter already tense relations between the two countries.

The alliance appeared near the breaking point in February when the burning of Qurans in a garbage pit at a U.S. base sparked protests and retaliatory attacks that killed more than 30 people, including six U.S. soldiers.

In recent days the two nations made headway toward an agreement governing a long-term American presence here, but the massacre in Kandahar province on Sunday has called all such negotiations into question.

Afghan lawmakers have demanded that the soldier be publicly tried in Afghanistan to show that he was being brought to justice, calling on President Hamid Karzai to suspend all talks with the U.S. until that happens.

The U.S. staff sergeant, who has not been named or charged, allegedly slipped out of his small base in southern Afghanistan before dawn, crept into three houses and shot men, women and children at close range then burned some of the bodies. By sunrise, there were 16 corpses.

The suspect was taken into custory shortly afterwards and at some point taken to Kandahar.

"We do not have appropriate detention facilities in Afghanistan," Navy Capt. John Kirby, a Pentagon spokesman, said on Wednesday.

He said that meant a facility for a U.S. service member 'in this kind of case'.

The U.S. military has detention facilities in Kuwait that have been used for other troops. Army PFC Bradley Manning was detained in Kuwait after he was taken into custody in Baghdad in 2010 for allegedly leaking government documents in the Wikileaks case.

Kirby said the transfer did not necessarily mean the trial would be held outside Afghanistan. U.S. officials had previously said it would be technically possible to hold proceedings in Afghanistan, noting other court-martial trials held here.

The decision to remove the soldier from the country may complicate the prosecution, said Michael Waddington, an American military defense lawyer who represented a ringleader of the 2010 thrill killings of three Afghan civilians by soldiers from the same Washington state base as the accused staff sergeant.

The prosecutors won't be able to use statements from Afghan witnesses unless the defense is able to cross-examine them, he said.

Waddington said the decision to remove the suspect was likely a security call.

"His presence in the country would put himself and other service members in jeopardy," Waddington said.

But the patience of Afghan investigators has already appeared to be wearing thin regarding the shootings in Panjwai district.

The soldier was caught on U.S. 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 on Wednesday there were also two to three hours of video footage covering the time of the attack that Afghan investigators are trying to get from the U.S. military. He spoke on condition of anonymity because of the sensitivity of the issue.

U.S. authorities showed their Afghan counterparts the video of the surrender to prove that only one perpetrator was involved in the shootings, the official said.

Some Afghan officials and residents in the villages that were attacked have insisted there was more than one shooter. If the disagreement persists, it could deepen the distrust between the two countries.

Panetta, in a series of meetings with troops and Afghan leaders on Wednesday, said the U.S. must never lose sight of its mission in the war, despite recent violence including what appeared to be an attempted attack near the runway of a military base where he was about to land.

It wasn't clear whether it was an attempt to attack the defense chief, whose travel to southern Afghanistan was not made public before he arrived. Panetta was informed of the incident after landing.

"We will not allow individual incidents to undermine our resolve to that mission," he told about 200 Marines at Camp Leatherneck. "We will be tested we will be challenged, we'll be challenged by our enemy, we'll be challenged by ourselves, we'll be challenged by the hell of war itself. But none of that, none of that, must ever deter us from the mission that we must achieve."

According the Pentagon spokesman, an Afghan stole a vehicle at a British airfield in southern Afghanistan and drove it onto a runway, crashing into a ditch about the same time that Leon Panetta's aircraft was landing.

The pickup truck drove at high speed onto the ramp where Panetta's plane was intended to stop, Kirby said. No one in Panetta's party was injured.