Australian soldiers in southern Afghanistan have shot dead two children tending cattle, officials say, in an incident likely to escalate tensions over the conduct of international troops.
Civilian casualties caused by NATO-led forces have been one of the most contentious issues in the campaign against Taliban insurgents, often triggering widespread public anger and harsh criticism from President Hamid Karzai.
The two children, aged seven and eight, were killed on Thursday morning as Australian soldiers fought back after a Taliban attack in Oruzgan province, provincial governor Amir Mohammad Akhundzada told AFP on Saturday.
"The children were killed by Australian troops, it was a mistaken incident, not a deliberate one," Akhundzada said, adding that insurgents had first shot at a helicopter carrying Australian soldiers.
NATO's International Security Assistance Force (ISAF) expressed its "deep regret" over the children's deaths and said it remained committed to minimising civilian casualties.
"I offer my personal apology and condolences to the family of the boys who were killed," General Joseph Dunford, commander of ISAF, said in a statement.
"I am committed to ensuring we do the right thing for the families of those we harmed, as well as for the community in which they lived. We take full responsibility for this tragedy."
ISAF said the troops had opened fire at what they believed were insurgent forces. It added that a joint Afghan-ISAF team visited the district of Shahidi Hassas in Oruzgan on Saturday to investigate and meet with local leaders.
Last month, 10 Afghan civilians, including five children, were killed by a NATO airstrike in Kunar province.
Following the attack, Karzai barred Afghan forces from seeking air support from foreign troops in a bid to curb civilian casualties.
Karzai has regularly lashed out at senior ISAF leaders, demanding that civilian deaths must be avoided and saying the killings have worsened relations between his government and the international coalition.
Previous civilian deaths caused by ISAF forces, especially those involving children, have brought protesters onto the streets of Kabul chanting slogans against the presence of international troops in Afghanistan.
Security responsibility for Oruzgan, a restive province where Taliban insurgents have been holding sway, is being handed over to Afghan forces.
The bulk of Australia's 1550 troops are based in the province, and are focused on training and mentoring Afghan soldiers ahead of the withdrawal of NATO combat troops by the end of next year.
Comment was being sought from Prime Minister Julia Gillard.