Afghan President Hamid Karzai called on the US military on Sunday to avoid operations that kill civilians, saying it was his "last warning" to Washington after 14 people allegedly died in an air strike.
Reacting to the alleged deaths of 10 children, two women and two men in an air strike on Saturday in the southern province of Helmand, Karzai said such incidents were "murdering of Afghanistan's children and women."
"The president called this incident a great mistake and the murdering of Afghanistan's children and women, and on behalf of the Afghan people gives his last warning to the US troops and US officials in this regard," his office said, adding that he "strongly condemned" the killings.
Citing initial "reports and heartrending pictures published on media" Karzai's office said 10 children, two women and two men were killed in the raid.
Adopting an unusually angry tone, Karzai said the US-led operations were "arbitrary" and unnecessary".
"The president said that US and NATO troops have been repeatedly told that their arbitrary and unnecessary operations cause the deaths of innocent Afghans and such operations violate human and moral values but it appears that (we) are not listened to," the statement said.
Local authorities in Helmand said that US Marines called in air support after their base in Nawzad district came under attack from small arms fire.
"During the air strike, two civilian houses were targeted which killed 14 civilians and six others were wounded," the provincial administration said in a statement.
The statement said the dead included five girls, seven boys and two women.
The NATO-led International Security Assistance Force said it was investigating the allegations.
"ISAF are aware of the reports that civilians were allegedly killed in an ISAF air strike," spokesman Major Tim James told AFP.
"(The) Regional Command South West has sent a joint assessment team to the area to look into the allegation and they will issue their findings to the press."
Footage and pictures from the troubled region showed turbaned men carrying the bodies of children and showing them to unseen journalists.
Aslam, a local elder of Nawzad district, told AFP he "lost 12 relatives while 10 others including children were injured" in the air strike.
He said some shots were fired at ISAF helicopters which flew into the area, adding that the choppers returned after 10 to 20 minutes and fired rockets, killing the "innocent civilians".
Separately the governor of Nuristan on Sunday told AFP that 18 civilians and 20 police were killed by "friendly fire" during US-led air strikes against insurgents in his troubled northeastern province.
Nuristan was the scene of heavy battles last week between the Taliban and Afghan security forces. The police and civilians were targeted Wednesday after they were mistaken for militants, Jamaluddin Badr said.
"The policemen were killed due to friendly fire," Badr said, adding the air strike in the troubled district of Do Ab targeted a location that the officers "had just" taken from the insurgents during fighting.
"Civilians were killed because the Taliban... (who) ran out of ammunition fled into the civilians' houses and then the civilians were mistaken with the Taliban and fired upon," the governor said.
Major James said those allegations were also being investigated.
"ISAF has sent a fact-finding team to investigate the allegations about civilian and police casualties in Nuristan," he said.
"Our initial reporting does not indicate civilian casualties in that air strike," he added.
The issue of civilian casualties is highly sensitive in Afghanistan as Karzai struggles to win the hearts and minds of his people against the Taliban.
The United Nations says Afghan civilian deaths in the war increased 15 percent to a record high of 2,777 last year. More than three-quarters of the dead were killed in violence blamed on insurgents.Afghans carry the bodies of people killed overnight after a raid by NATO and Afghan forces, during a protest in Taloqan May 18, 2011. Ten people have been killed and fifty wounded in violent protests against the killing of two men and two women in a night-time raid in north Afghanistan, a top local health official said.« Read less REUTERS/Stringer (AFGHANISTAN - Tags: CIVIL UNREST POLITICS)