A U.S. Army staff sergeant is suspected of leaving his base and killing nine Afghan children, three women and four men in two villages in southern Afghanistan last weekend.
The Taliban, in a statement, said they wouldn't be content with anything but revenge for the attacks on the "oppressed countrymen."
"We shall cut off the heads of your murderous sadistic troops in every corner of the country in revenge for the martyrdom of every single Afghan and we shall not desist from utilizing any means for this purpose," the Taliban said.
Anti-American sentiment in Afghanistan is already high following the alleged mishandling of the Koran last month. U.S. officials expressed remorse but vowed to continue with the mission.
U.S. Secretary of State Hillary Clinton said from the U.N. headquarters that a full investigation into the weekend incident was under way.
"We've had a difficult and complex few weeks in Afghanistan. That is obvious to everyone," she said. "This terrible incident does not change our steadfast dedication to protecting the Afghan people and to doing everything we can to help build a strong and stable Afghanistan."
The Taliban, in their statement, said "American invaders" made "empty apologies" in an effort to absolve themselves of any crime.
"Instead of seeking forgiveness from the families of the victims, it sent apologies to its puppet [Afghan President Hamid] Karzai, which in itself is a crime and which will not be accepted by the Afghan people in any circumstance," the statement read.