ASADABAD: Two of Nasim's sons went into the hills to collect firewood last week to warm the family's humble home against the biting Afghan winter chill. They never returned, killed along with seven other children in a Nato air strike.

“The Americans are wild,” said the boys' father, who uses only one name and whose sons were aged 11 and 12, crying as he spoke. “They don't value humanity and don't care about our children.

“The men who carried out the air strike and the ones who ordered it should be brought to court.”

The nine killings outside Asadabad in Kunar province have unleashed public fury over civilian casualties at a crucial time for foreign forces in Afghanistan.

The accidental deaths led the US troop commander in Afghanistan, General David Petraeus, to issue a rare public apology, while US President Barack Obama also voiced “deep regret” to Afghan counterpart Hamid Karzai.

The International Security Assistance Force (ISAF) says those responsible could face disciplinary action.

But that may not be enough to stem growing Afghan anger at a time when the battle for hearts and minds is keener than ever, with foreign forces due to start handing over control of security to their Afghan counterparts in July.

The deaths in Kunar, a troubled northeastern province bordering Pakistan, happened on Tuesday as troops fought back after an insurgent rocket attack on their base.

Civilian casualties in foreign military operations targeting the Taliban and other fighters have long been an issue in Afghanistan.

Karzai has repeatedly issued angry condemnations of foreign forces over such deaths. Last week he went further still, warning them they would face “huge problems” if the “daily killing of innocent civilians” did not stop.

The United Nations' special representative for children and armed conflict, Radhika Coomaraswamy, also called for a “thorough review of procedures” to prevent the deaths of children in the Afghan war following the incident.

Around 150 people held protests in Asadabad, the capital of Kunar, on Wednesday and more demonstrations were expected in Kabul on Sunday.

ISAF says it does all it can to prevent civilian casualties during a counter-insurgency in which winning the hearts and minds of Afghans in poor, rural areas is seen as key by commanders.

A tactical directive issued by Petraeus shortly after he took up his job last year stipulates that commanders must establish that no civilians are close by before launching an attack.

“Every Afghan civilian death diminishes our cause,” the directive says. “We must never forget that the center of gravity in this struggle is the Afghan people.”

But for ordinary Afghans, the sensitivity of the issue is due partly to a perception that, for international forces,“Afghan people's blood is of no value,” according to Kabul-based political analyst Waheed Mujda.

“For the Americans, apologising for a mistake is a very big deal but for Afghans it is not,” he said. “ISAF troop actions that raise anger among Afghans are a major reason for people joining the insurgents or Taliban.”

Afghan officials insist that when their forces take full charge of security across the country in 2014, such incidents will occur less frequently.

“Currently, the biggest problem in the war against terrorism for the Afghan government is civilian casualties,” defence ministry spokesman General Zahir Azimi told AFP.

“Afghan troops are aware of the geography, the terrain, the people and are familiar with the operation areas. They know the enemy and will just engage the enemy, not civilians.”

Human rights watchdog the Afghanistan Rights Monitor said last month that at least 217 civilians died in air strikes by international forces in 2010.

That comes against a backdrop of increasing civilian deaths overall in the Afghan war.

UN figures show the figure for the first ten months of 2010 rose 20 per cent on the previous year, to 2,412.

But more than three-quarters of them were linked to insurgents, the UN said, while the numbers linked to international and Afghan government forces decreased by 18 per cent.

The statistic is of no comfort to the families of Asadabad.

Subhan, who like Nasim had two sons killed in the attack and also only uses one name, said: “The Americans came over to my home and spoke to us, saying they apologise. But that is not acceptable for us.”