A mourner cries over the bodies of the Afghan civilians, shot by US forces, in the Alkozai village in Kandahar Province in southeastern Afghanistan on March 11, 2012.
Afghan eyewitnesses say US troopers have burnt nearly a dozen bodies of the Afghan victims, whom American servicemen had killed during an earlier massacre.
Early Sunday, US forces opened fire on Afghan civilians inside their homes in the district of Panjwaii in the southern province of Kandahar, killing at least 17 civilians and injuring several others. The Taliban militants said at least 50 people were killed in the massacre.
Earlier reports said the assassin was a lone US sergeant.
Villagers said the US forces later collected 11 of the bodies, including those of four girls under the age of six, and set them on fire.
Afghan President Hamid Karzai has condemned the bloodshed, calling it an inhuman, intentional, and unforgiveable act.
“When Afghan people are killed deliberately by US forces, this action is murder and terror and an unforgivable action," Karzai said in a statement.
"The government and the people of Afghanistan demand an explanation from the United States government of this incident."
Civilian casualties in Afghanistan have been a major source of tension between Kabul and Washington.
The outrages came in the wake of violent clashes in several Afghan provinces over recent desecration of the Holy Qur’an by the United States forces at the US-run Bagram Airbase in the province of Parwan in northeastern Afghanistan. The violence left over 30 people, including six American forces, dead and around 180 others injured.
The US-led invasion of Afghanistan was launched in 2001. The offensives removed the Taliban from power, but insecurity continues to rise across the country, despite the presence there of tens of thoUSands of US-led troops.