KANDAHAR, Afghanistan (AFP) - Survivors and victims' relatives on Thursday voiced fury that the US soldier who massacred 16 Afghan villagers last year would escape the death penalty after pleading guilty.

Sergeant Robert Bales admitted 16 counts of murder in a packed courtroom in Washington state on Wednesday over the killings in March 2012 that caused outrage in Afghanistan and plunged US-Afghan ties to a new low.

Military Judge Colonel Jeffery Nance accepted the guilty pleas, and ruled that Bales, 39, would face a maximum of life behind bars without eligibility for parole.

"All I want is to see this guy executed. We don't want anything else," said Mr Samiullah, who lost his mother in the massacre that also left his daughter Zardana and his son Rafiullah wounded.

Zardana, now about 12, has a paralysed arm and leg despite four months of medical treatment in the US.

"I went home and found my mother dead lying on the floor of the room in her blood," Mr Samiullah told AFP.

"My daughter Zardana was hit in the arm and leg. She was lying in her blood too, my son also. Nothing else will satisfy us but the execution of this man.

"He has shot my children, killed my mother and we want him to be executed."

Haji Naeem, another villager from the Panjwai district of Kandahar province where Bales ran amok, was wounded along with his young son and two of his daughters.

"See what they have done to me," he told AFP. "I can't move my arm. The Americans will do what they want. Only his execution will heal our pains. We want him to be executed, and executed in Afghanistan."

But Mr Abdul Baqi, Haji Naeem's nephew, acknowledged: "What we want will not happen. They should execute him, not jail him."

Bales' lawyer John Browne said he hoped his client, who will be sentenced in August, could be out of jail after 10 years.

In court at Joint Base Lewis-McChord south of Seattle, Bales said he had no explanation for why he opened fire on the villagers using an M4 rifle and a 9mm pistol.

Seventeen of the 22 victims were women or children and almost all were shot in the head.

"I formed the intent to kill and then did kill by shooting with a firearm and burning," he said, repeating the phrase for each of the 16 murder counts against him.

Asked why he had killed the villagers, he said: "Sir, as far as why, I've asked that question a million times since then. There's not a good reason in this world for why I did the horrible things I did."