Three US soldiers were killed Friday in attacks in Afghanistan, NATO said, as Afghan authorities accused international forces of killing six children during an air assault on Taliban positions.

Amid a surge in military deaths, NATO's International Security Assistance Force (ISAF) said it lost three soldiers in two separate Taliban-style bomb attacks -- two were killed in the country's east, while one died in the south.

The insurgency, dragging towards its tenth year, is concentrated in the eastern and southern border belts of the country.

In eastern Kunar province, a mountainous region known to be a Taliban stronghold, a police commander told AFP that six children were killed in an air raid aimed at quelling a Taliban attack.

Provincial police chief Khalilullah Ziayee said a group of children were collecting scrap metal on the mountain when NATO aircraft dropped bombs to disperse Taliban fighters attacking a nearby base.

"In the bombardment six children, aged six to 12, were killed. Another child was injured," the police commander said.

ISAF said in a statement that it had carried out an airstrike and it was investigating claims that civilians had been killed in those raids.

ISAF "officials are aware of civilian casualty allegations as a result of the engagement and are conducting an investigation," it said in a statement.

The alliance force said its soldiers observed a rebels' round killing a non-combatant in a cornfield as it fought the militants from a small outpost. It said four rebels were also killed in the battle.

The issue of civilian casualties is highly sensitive with Afghan leaders who argue that such incidents erode public support for the Western-backed administration.

In a recent meeting with US congressmen and military officials, President Hamid Karzai said one of the reasons that the US-led "war on terror" had not yet succeeded was "because civilians were killed in this war".

Kunar, a rugged and heavily wooded region, is one of the most troubled provinces in Afghanistan and the scene of a huge military operation by US-led forces and their Afghan counterparts earlier in the summer.

The US-led force has been responsible for scores of civilian deaths, mainly caused by air raids during battles with Taliban and other insurgents.

Violence has picked up in Afghanistan in recent months, coinciding with the deployment of 30,000 additional US troops to reinforce the battle against the Taliban under Washington's Afghan counter-insurgency strategy.

The surge in violence has led to increased military deaths. With Friday's casualties, the number of foreign soldiers killed in Afghanistan this year reached 465, compared to 521 for all of 2009, according to independent tallies.

There are nearly 150,000 US-led foreign troops in Afghanistan fighting to reverse an escalating Taliban-led insurgency and to train Western-backed Afghan government forces so they can take responsibility for national security.

ISAF meanwhile said Friday it wrapped up a significant military push against the Taliban around Kabul.

Involving hundreds of US, French and Afghan troops, the operation was aimed at securing the area ahead of a September parliamentary election.

About 40 rebels were killed during the offensive launched on August 21, ISAF said in a statement.