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".

French troops are said to operate in the area.

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