The US-led NATO force in Afghanistan on Monday conceded that several children died during a bombing raid last week in the northeast province where French troops are based.

Afghan President Hamid Karzai had condemned the air strikes and ordered an investigation after saying that eight children were killed on February 8.

Brigadier General Carsten Jacobson, spokesman for the International Security Assistance Force (ISAF), said that an ongoing assessment showed that troops engaged "a group of men, who were armed and engaging in unusual behaviour".

"This group was engaged by coalition aircraft and that engagement followed all ISAF tactical directives. Following the engagement, additional casualties were discovered and these casualties were young Afghans of varying ages.

"At this point in our assessment, we can neither confirm nor deny, with reasonable assurance, a direct link to the engagement," he said.

But Mohammad Tahir Safi, a member of parliament for Kapisa and part of the investigation team dispatched by Karzai, disagreed.

To reporters, he narrated an account in which the local head of Afghan intelligence told a French colonel that the area of the planned operation was "not a threat", refusing to countenance an operation.

Safi said French troops raided the homes of two former jihadi commanders before dawn, confiscating "only one mortar round, a shotgun... some AK rounds and nothing else".

About 600 metres west of the village, children gathered to start a fire when "all of a sudden a plane dropped one bomb in first round and another bomb later", he said, showing pictures of bloodied children in shrouds.

"There were eight people and all innocent children and you can see their pictures," he said. The dead were aged between six and 14, with "another guy aged about 18 to 20" who was mentally ill, Safi said.

Jacobson called any deaths of innocent people a tragedy but insisted: "We simply are not yet certain how this happened."

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.

At the time, Kapisa district police chief Abdul Hamid Erkin told AFP that seven children and a mentally-handicapped 20-year-old were killed.

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

Last month, French President Nicolas Sarkozy said troops would hand over responsibility for security in Kapisa to Afghans from March 2012, following the killing of four French soldiers by an Afghan they were training.