A NATO airstrike killed eight children in Afghanistan's Kapisa province northeast of the capital Kabul, President Hamid Karzai said Thursday.

The president "strongly condemned the aerial bombing by foreign troops that killed a number of children in Nejrab district" on Wednesday, said a statement from his office.

"Based on information by (the) provincial governor, as a result of an air strike conducted on February 8... eight children were killed," the statement said.

Karzai had assigned a delegation "to launch an all-out probe into the NATO bombing in the province of Kapisa", it added.

A NATO spokesman said he could "confirm there has been a situation. A joint assessment team went there to identify the situation".

The Afghan president, who has a strained relationship with his Western allies, has regularly condemned NATO for civilian deaths in the decade-long war against Taliban insurgents fighting to overthrow him.

Kapisa district police chief Abdul Hamid Erkin told AFP: "Two nights ago foreign special forces carried out a raid on a house in Geyawa village in Nejrab district.

"The next morning their plane carried out an airstrike on a house in the village as a result of which seven children and one adult were martyred."

He said commanders of French troops who operate in the area "claimed that the target was a group of Taliban facilitators, but we checked the area and there were no Taliban.

"In fact the people in the area have very strong anti-Taliban feelings. We filmed the victims, who were children, and showed it to the French commanders," Erkin said.

The children were aged between about seven and 15, he said, while the adult was a mentally-handicapped 20-year-old.

Four French soldiers were gunned down by a renegade Afghan soldier in the Kapisa area last month, prompting President Nicolas Sarkozy to announce that France would pull out its troops by the end of 2013, a year before the international deadline for a withdrawal of combat forces in 2014.

France has some 3,600 soldiers among NATO's 130,000 troops fighting alongside government forces against the Taliban insurgency.

A record number civilians were killed in Afghanistan in 2011, the fifth straight year the death toll has risen, the United Nations reported last week.

A total of 3,021 civilians died -- mostly at the hands of insurgents -- up eight percent from 2,790 in 2010, the UN mission in Afghanistan (UNAMA) said in its annual report.

Taliban-led insurgents caused 77 percent of the deaths last year, up 14 percent from 2010, while pro-government forces were responsible for killing 410 civilians -- 14 percent of the total, the report said.

Most deaths attributed to NATO forces were a result of attacks from the air, but there was an overall decline of four percent in the number of civilians killed by pro-government forces, the report said.