The US military said its investigators could not conclusively determine the number of people killed in the fighting.

Raids by US fighters aircraft had targeted buildings where suspected Taliban fighters were regrouping after a series of clashes, it said.

The death toll presented by the Afghan authorities would make the Bala Buluk clashes the deadliest incident for Afghan civilians since the US-led invasion in 2001.

The US military had previously acknowledged that "a number" of civilians were killed, but said it was impossible to say how many because all the bodies were buried before investigators arrived.

Fresh civilian deaths

The US military statement came on the same day the Nato-led force in Afghanistan announced that an air raid by one of its fighter jets had killed eight civilians in the southern province of Helmand.

The statement said the raid was launched after a clash with a group of 25 fighters in on Tuesday.

It accused the fighters of using civilians as human shields during the battle.

Elsewhere in the country, two Americans, including a soldier, were killed in an suicide bomb attack on a US military convoy, according to officials.

The convoy was travelling between the US air base at Bagram and the north of Kabul, the Afghan capital, when it was hit on Wednesday.

One American soldier and a US civilian working for the military were killed, an US military official said.

Barack Obama, the US president, has promised to address Afghanistan's long-term stability during his time as commander-in-chief, pledging thousands more US troops to the country.

Khalilzad denial

In a separate development, Zalmay Khalilzad, a former US ambassador to the UN and Afghanistan, has denied reports that he is not looking for a post in the Afghan government.

The New York Times newspaper quoted diplomats and US officials on Tuesday as saying that Hamid Karzai, the Afghan president, mentioned the idea of a high-level position in the Afghan government for Khalilzad during recent meetings with senior aides to President Obama.

Khalilzad said he had not left the US since Karzai was in Washington earlier this month. "Obviously I care about Afghanistan," he told The Associated Press news agency.

"I've always said that I would help. That shouldn't be taken that I was a candidate for president or a candidate for the CEO job.

"I am not looking for a job for myself in the government of Afghanistan. I'm not negotiating with Karzai for a position for CEO."