Blood-spattered walls

The walls of the house were blood-splattered.  

"They (Americans) poured chemicals over their dead bodies and burned them," Samad told Reuters at the scene.

Neighbors said they had awoken to crackling gunfire from American soldiers, who they described as laughing and drunk.  

"They were all drunk and shooting all over the place," said neighbor Agha Lala, who visited one of the homes where killings took place.

"Their (the victims') bodies were riddled with bullets."  

An Afghan National Army soldier keeps watch inside a US base in Panjwai district Kandahar province, March 11, 2012. [Photo/Agencies]

A senior US defense official in Washington rejected witness accounts that several apparently drunk soldiers were involved. "Based on the preliminary information we have this account is flatly wrong," the official said. "We believe one US service member acted alone, not a group of US soldiers."

Defense Secretary Leon Panetta called Karzai to offer his condolences. "I condemn such violence and am shocked and saddened that a US service member is alleged to be involved, clearly acting outside his chain of command," Panetta said in a statement. "A full investigation is already under way. A suspect is in custody and I gave President Karzai my assurances that we will bring those responsible to justice."

The Afghan Taliban said it would take revenge for the deaths, in an emailed statement to media.  

The US Embassy in Kabul said an investigation was under way and that "the individual or individuals responsible for this act will be identified and brought to justice."

ISAF Commander General John Allen promised a rapid investigation.  

Civilian casualties have been a major source of friction between Karzai's Western-backed government and US-led NATO forces in Afghanistan. NATO is preparing to hand over all security responsibilities to Afghans and all foreign combat troops are scheduled to leave by end-2014.

NATO Secretary General Anders Fogh Rasmussen said the alliance remained firmly committed to its mission and said anyone responsible would be held accountable.

The Koran burning and the violence that followed, including a spate of deadly attacks against US soldiers, underscored the challenges that the West faces as it prepares to withdraw.  

Sunday's attack may harden a growing consensus in Washington that, despite a troop surge, a war bill exceeding $500 billion over 10-1/2 years and almost 2,000 US lives lost, prospects are dimming for what the United States can accomplish in Afghanistan.

"These killings only serve to reinforce the mindset that the whole war is broken and that there's little we can do about it beyond trying to cut our losses and leave," said Joshua Foust, a security expert with the American Security Project.

Afghan National Army soldiers keep watch as Afghans gather outside a US base in Panjwai district Kandahar province, March 11, 2012. [Photo/Agencies]