The Taliban has vowed revenge against "sick-minded American savages" after a U.S. soldier was accused of going on a deadly shooting rampage Sunday.
The group said it would "take revenge from the invaders and the savage murderers for every single martyr," according to a statement posted on its website, the Times of London reported.
An Army veteran of three tours in Iraq who left his base in the middle of the night is suspected of methodically killing 16 Afghan civilians, most of them children and women.
The soldier's name has not been released, but a U.S. official told ABC News he is a 38-year-old staff sergeant who is married with two children. He is apparently based at Fort Lewis in Washington state.
The soldier wore night-vision goggles during the alleged rampage and has "lawyered up" and declined to talk, according to a source.
The fear now is that this latest incident could set off a fresh wave of violence.
The attack comes just as outrage stemming from burning of several Korans by members of the U.S. military seemed to be calming down.
The U.S. Embassy in Kabul has warned foreigners to keep a low profile.
Afghan President Hamid Karzai called it "an assassination, one that cannot be forgiven."
The Afghan parliament has passed a resolution in protest of the killings, and asked for a public trial of the U.S. soldier.
U.S. officials were quick to condemn the attack Sunday.
"I offer my profound regret and deepest condolences to the victims and their families," Gen. John Allen, head of NATO forces in Afghanistan, said in a statement.
"This deeply appalling incident in no way represents the values of ISAF [International Security Assistance Force] and coalition troops or the abiding respect we feel for the Afghan people."
Shooting in Afghanistan
The shooting took place at 3 a.m. in two villages in the Panjwai district of southern Kandahar province, a hotbed for the Taliban insurgency against U.S .forces.
The two villages are a short walk away from the U.S. base where the soldier was stationed.
Nine of the victims were children, and three were women, all shot while they slept in their beds, according to villagers and the Afghan president's office.
Photos from the scene show blood-splattered floors and walls inside a villagers home, one of three believed to have been attached, and blood-soaked bodies of victims, including the elderly and young children, wrapped in blankets and placed in the backseat of a van. Some of the bodies appear to have been burned.
John Kirby, a Pentagon spokesman said officials "don't know what his [soldier's] motivation was, we are looking into that."
After the alleged shooting spree, it's believed the soldier returned to the base on his own, and calmly turned himself in. He remains in NATO custody.
It's unclear whether the soldier knew the victims or whether the alleged attack was spontaneous and unprovoked. It's also unknown whether he had any accomplices.
This was his first tour in Afghanistan, where he has been since early December, the official said.
NATO has launched its own investigation, and Karzai has sent his delegation to Kandahar for its own inquiry.
The White House said Sunday that Obama called "President Karzai to express his shock and sadness at the reported killing and wounding of Afghan civilians. President Obama extended his condolences to the people of Afghanistan, and made clear his Administration's commitment to establish the facts as quickly as possible and to hold fully accountable anyone responsible. The president reaffirmed our deep respect for the Afghan people and the bonds between our two countries."