KABUL — Afghan President Hamid Karzai spoke out for the first time Wednesday about the "heart-rending" media accounts of a rogue US army unit accused of deliberately killing civilians for sport.

In his first public reaction to the scandal, Hamid Karzai said he wanted to ensure ordinary Americans knew about an alleged rogue army unit "kill team" accused of murdering Afghan civilians and mutilating their corpses.

Karzai said he was disturbed by the accounts in US media of American soldiers deliberately killing children and elderly Afghans who posed no threat to them.

"They killed our youths for fun, they killed old people, they even planned to kill children," Karzai said in a speech to a group of newly-qualified teachers in Kabul.

"I want the ordinary American people to hear my voice and to know that Afghans old and young are being oppressed in their name."

Rolling Stone magazine this week published a series of graphic images and a long story including extensive detail of the allegations against the American soldiers.

The story related how a teenage farm worker was picked out in January last year as the first victim of an allegedly drug-addled rogue unit that slaughtered Afghan civilians in the explosive Kandahar region early last year.

Two soldiers, one of whom was last week jailed for 24 years, initially threw a grenade at the teenager before gunning him down, and pretending the youth had attacked them with the grenade.

A photograph accompanying the story shows the little finger of the boy's right hand is missing, allegedly cut off as a trophy.

In the following months they and others staged a number of such killings, according to the Rolling Stone account, citing witnesses questioned by military investigators after the killings were revealed by a fellow soldier.

"I read all nine pages last night. It was a heart-rending story," said Karzai. "May God punish them."

The US military has apologised for the distress caused by the pictures, which recall the notorious Abu Ghraib prison abuse images from Iraq.

A Pentagon statement said they were "in striking contrast to the standards and values of the United States Army."

Altogether a dozen soldiers, all members of Bravo Company, 2nd Battalion, 1st Division's Stryker brigade, based in the volatile Kandahar region of southern Afghanistan, are accused of various crimes in the case.