US soldier Staff Sgt Robert Bales has pleaded guilty to killing 16 Afghan civilians, mostly women and children in March last year.
His plea means that Bales will not be executed, but will be sentenced to life with or without the possibility of parole.
Residents of the village where the massacre took place and relatives of the victims have reacted with outrage at what they say is a lenient sentence.
"It is our firm demand that Afghanistan, the US and the international community condemn this American to death. He martyred our family members... and went back with his body full of blood of his victims to his camp," villager Mullah Baran told the BBC.
Another villager, Haji Baqi, whose brother was killed by Bales, said: "We want him to be hanged. The international community should not ignore our grief."
Bales pleaded guilty at a hearing on Wednesday, where he detailed each killing in the same terms.
"I left the VSP [Village Stability Platform] and went to the nearby village of Alkozai. While inside a compound in Alkozai, I observed a female I now know to be Na'ikmarga. I formed the intent to kill Na'ikmarga, and I did kill Na'ikmarga by shooting her with a firearm. This act was without legal justification, sir."
When asked why he had carried out the murders, said: "There's not a good reason in this world for why I did the horrible things I did.”
