NATO probes report of child killed in Afghan airstrike

US-led NATO forces in Afghanistan on Friday vowed to investigate an airstrike that President Hamid Karzai said killed a two-year-old boy, as acrimony deepens over a deal to allow US troops to stay in the country after 2014.

Civilian casualties have been one of the most sensitive issues of the 12-year military intervention in Afghanistan, and Karzai warned that the latest incident threatened the proposed bilateral security agreement (BSA) with Washington.

The NATO coalition acknowledged reports of the boy's death and said it "deeply regrets any civilian casualties caused by this airstrike" on Thursday in the southern province of Helmand, a hotbed of the Taliban insurgency.

Karzai, whose troubled relationship with the US has again erupted in public over the security agreement, has often used civilian deaths caused by NATO to berate the international coalition for its failures in Afghanistan.

"President Hamid Karzai strongly condemns the airstrike by NATO forces on a house which killed one child and wounded two women," a statement from his office said late Thursday.

"This attack shows American forces are not respecting Afghan lives... As long as unilateral acts and atrocities continue by American forces on our people, we won't sign this BSA."

The airstrike was launched from an unmanned drone and hit the village of Faqiran in Helmand on Thursday morning, the statement said.

NATO's International Security Assistance Force said that the strike targeted an insurgent riding on a motorbike, but it did not confirm that a drone was involved.

Karzai, who is due to step down ahead of presidential elections in April, has been stalling over the security pact with Washington that would see some US troops to remain in Afghanistan after next year for training and counter-terror missions.

Helmand provincial spokesman Omar Zwak told AFP that the child, called Rafiullah, had died in a strike targeting a Taliban commander.

Zwak said a second drone attack killed the commander.