KANDAHAR - The killing of Afghan civilians by an American soldier who went on a house-to-house shooting spree in southern Afghanistan has sent shockwaves across the Asian Muslim country.
"When Afghan people are killed deliberately by US forces, this action is murder and terror and an unforgivable action," Afghan President Hamid Karzai said, Agence France-Presse (AFP) reported.
At least 16 Afghan civilians were killed by a US soldier, who walked off his base and broke into homes of villagers in two villages in Kandahar province's Panjwayi district.
Among those killed were three children and nine women.
Some bodies bore blackened burn marks, according to an AFP correspondent who saw them.
"He came to my uncle's home, he was running after women, he was tearing their dresses, insulting them," Rafihullah, a 15-year-old boy, 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," added the Afghan boy, who was injured in the lege.
The US military said that the soldier suffered a nervous breakdown before going into his shooting spree.
The killings have sparked angry vows from the Taliban for revenge.
The Taliban threatened to take revenge against "sick-minded American savages ... for every single martyr," according to a statement on their website cited by AFP.
"A large number from amongst the victims are innocent children, women and the elderly, martyred by the American barbarians who mercilessly robbed them of their precious lives and drenched their hands with their innocent blood.
"The American 'terrorists' want to come up with an excuse for the perpetrator of this inhumane crime by claiming that this immoral culprit was mentally ill, the group said.
"If the perpetrators of this massacre were in fact mentally ill then this testifies to yet another moral transgression by the American military because they are arming lunatics in Afghanistan who turn their weapons against the defenseless Afghans without giving a second thought.
Seeking to prevent a further deterioration in US-Afghan ties, President Barack Obama telephoned Karzai to promise a speedy investigation into the killings.
"I am deeply saddened by the reported killing and wounding of Afghan civilians. I offer my condolences to the families and loved ones of those who lost their lives, and to the people of Afghanistan, who have endured too much violence and suffering," Obama said, CNN reported.
"This incident is tragic and shocking, and does not represent the exceptional character of our military and the respect that the United States has for the people of Afghanistan."
In a separate statement, Defense Secretary Leon Panetta said he was "shocked and saddened" by the attack.
He also assured the Afghan president in a phone call that a "full investigation" was under way.
"A suspect is in custody, and I gave President Karzai my assurances that we will bring those responsible to justice," Panetta said.
Acting US Ambassador James Cunningham also said his country was "saddened by this violent act against our Afghan friends."
"We deplore any attack by a member of the US Armed Forces against innocent civilians," he said in a video statement, assuring "the people of Afghanistan that the individual or individuals responsible for this terrible act will be identified and brought to justice," he said.
The Kandahar massacre came after Afghan laborers found charred copies of the Noble Qur'an while collecting rubbish at Bagram airbase in Kabul last month.
The burning sparked deadly protests across Afghanistan, which left at least 30 people dead.
Obama and NATO commanders have apologized for the Qur'an burning, describing it as a mistake.
But, Sunday's massacre, the latest American public relations disaster in Afghanistan, could be a turning point for the US, which wants to maintain advisers there as it tries to wind down the increasingly unpopular war.
The Strategic Partnership Agreement currently being negotiated is a key part of that strategy."This could delay the signing of the Strategic Partnership Agreement," an Afghan government official told Reuters on Monday.