Afghan President Hamid Karzai has "strongly condemned" a NATO air strike that killed at least eight children in eastern Afghanistan.

An investigation has been launched into the incident, which took place in Geyawa village in the Nejrab district of Kapisa province on Wednesday, a palace statement said.

Karzai has assigned a delegation led by adviser Haji Mohammad Zaher Safi and a number of MPs and representatives from various Afghan ministries to launch "an all-out probe into the NATO bombing", the statement said.

"President Karzai contacted the provincial governor and inquired more on the incident and telephoned the mourning families and expressed his deepest sympathies and condolences," the statement said.

Lieutenant Commander James Williams, a spokesman with the NATO-led international forces confirmed the incident saying a joint NATO assessment team was investigating the circumstances.