A witness from the village, in Uruzgan province, told the BBC the overnight raid left scores of people - many of them women - dead.

Afghan officials in the capital, Kabul, put the death toll at at least 30, although other reports say the figure is much higher.

In Washington, a military spokesman said a coalition air reconnaissance patrol flying in the area had reported coming under anti-aircraft artillery fire.

The Pentagon said other coalition aircraft in the patrol retaliated and acknowledged there had been an error.

"At least one bomb was errant. We don't know where it fell," he said.

An AC-130 gunship, a B-52 bomber and other aircraft were involved in the incident.

Afghan leader Hamid Karzai said aid was being organised for the area and a commission had been set up to investigate the incident.

Some reports suggest that the American planes may have mistaken gunfiring at the wedding for hostile fire aimed at them.

Afghans often fire guns in the air during weddings and other celebrations.

An investigation has also been launched by the US military.

A US military spokesman added that four injured civilians had been airlifted to hospital by US forces.

A resident from the bombed area, Abdul Saboor, told the BBC: "There was no-one to help last night.

"We managed to transfer some of the wounded to Kandahar in the morning. Some of the foreigners' choppers also came to help.

"There are no Taleban or al-Qaeda or Arabs here. These people were all civilians, women and children."

- Children orphaned

At the Mir Wais hospital in Kandahar, staff said they had been told most of the dead were women and children.

Nurse Mohammed Nadir said: "The villagers brought these children and they have no parents.

"Everyone says that their parents are dead."

One six-year-old girl was brought to the hospital still wearing her party dress.

She was injured, and villagers said all members of her family were killed.

- Targeting errors

US forces operating in Afghanistan have made a number of errors during the campaign against the Taleban and al-Qaeda forces.

- Four Canadian soldiers were killed in April when a US fighter bombed them by mistake during a training exercise.

- In January, US bombs killed civilians in the village of Hazar Qadam, targeted as a Taleban compound.

- In December, planes bombed a convoy from the eastern town of Khost, killing people Mr Karzai said were tribal elders travelling for his inauguration.

- Last October, a targeting error led to a bomb hitting a residential area of Kabul, instead of a helicopter at the airport.