Outrage over a murderous rampage by a rogue American soldier who killed 16 villagers gripped Afghanistan Monday as parliament called for a public trial and Taliban insurgents vowed revenge.

The United States embassy issued fresh warnings to its citizens of possibly violent protests but the White House insisted US strategy in Afghanistan would not change despite the fresh jolt to America's war policy.

The American walked off his base in southern Kandahar province and broke into three village homes before dawn Sunday, killing 16 people including women and children -- an event described by Afghan President Hamid Karzai as "unforgivable".

"We seriously demand and expect that the government of the United States punish the culprits and try them in a public trial before the people of Afghanistan," parliament said in statement before closing for the day in protest.

Condemning the killings as "brutal and inhuman", parliament declared that "people are running out of patience over the ignorance of foreign forces".

But the Pentagon rejected calls for a public trial.

Investigations, and where warranted, the prosecutions of US service members are governed by "agreements in place with the government of Afghanistan," spokesman George Little said.

The US Army sergeant alleged to have committed the killings is in his 30s, according to Little. He served three tours of duty in Iraq and this was his first deployment to Afghanistan.

"We believe that this was a lone US servicemember who was involved in this deeply tragic set of shootings," Little said.

Sunday's incident is the latest in a series of actions by troops that has provoked outrage in Afghanistan, and comes just weeks after the burning of Korans at a US base sparked riots that killed 40 people and plunged ties to an all-time low.

The Taliban, leading a 10-year insurgency against US-led foreign troops and the government in Kabul, threatened to take revenge against "sick-minded American savages".

Braced for the worst, the US embassy urged its citizens in Afghanistan to take extra precautions.

But there were no reports of protests by evening Monday, and community leaders in Kandahar appeared to be trying to prevent any outbreak of violence.

US President Barack Obama telephoned Karzai to promise a speedy investigation into the "shocking" killings, and an American soldier is in military detention over the shootings.

US Secretary of State Hillary Clinton said she was "shocked and saddened" but White House spokesman Jay Carney said US strategy would remain on course despite the "challenging time".

"Our strategic objectives have not changed and they will not change," he said, adding Washington remained committed to disrupting, disarming and defeating Al-Qaeda and training Afghans to ensure their own security.

Sunday's massacre poses an acute test of the US-Afghan alliance, as the two countries pursue difficult talks on securing a strategic pact to govern their partnership once foreign combat troops leave Afghanistan in 2014.

Any deal would address the legal status of US troops who may remain to help prevent the country falling back into the hands of the Taliban, who were toppled in 2001 for sheltering Al-Qaeda leader Osama bin Laden.

Karzai spoke by telephone with the families of those killed, including Rafihullah, a 15-year-old boy wounded in the leg who told the president the soldier had torn the dresses of the women in the house and insulted them.

"He came to my uncle's home, he was running after women, he was tearing their dresses, insulting them," Rafihullah said on an audiotape of the conversation heard by AFP.

"He killed my uncle and killed our servant and killed my grandma, he shot dead my uncle's son, his daughter," the boy said.

The Taliban wasted no time in trying to capitalise on the killings, sending fighters to mosques in Kandahar's Panjwayi district as the funerals of the victims of the shootings took place, urging villagers to rise up.

"They were telling the people: 'The invading infidel Americans come to your homes, insult your women and kill your children, what are you waiting for? You should come out and demonstrate'," local resident Abdul Khaliq told AFP.

Kandahar is a stronghold of the Taliban fighting to oust Karzai's government, which is supported by 130,000 US-led NATO troops.

Afghan resentment of US forces was also provoked in January by a video posted online showing US Marines urinating on the bloodied corpses of slain Afghan insurgents -- an incident condemned by the Pentagon.

In November, the ringleader of a rogue American "kill team" charged with murder for shooting civilians for sport was found guilty and sentenced to life in prison by a military panel.

But the vast majority of civilian deaths in the Afghan war are attributed to the Taliban. A total of 3,021 civilians died in the war last year, according to a UN report, which blamed 77 percent of the deaths on the militia.

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