American troops have returned to an Afghan village to investigate claims that special forces killed up to 16 civilians they mistook for al-Qa'ida fighters during a night raid.
The US Defence Secretary, Donald Rumsfeld, has admitted for the first time that the assault by special forces and Navy Seals might have resulted in "unfortunately killing or wounding some individuals who might have been friendly".
He said he had no information about claims that American forces were handing out $1,000 (£700) in compensation to the families of those killed.
The raid took place on a village in Uruzgan province, south of Kandahar, on 24 January, resulting in 15 or 16 deaths and the arrest of 27 people.
The Pentagon initially claimed the raid had been intended to destroy an ammunition dump believed to have been used by al-Qa'ida or Taliban forces still holding out in the area.
Villagers claimed, however, that those killed were members of a delegation sent by the interim Afghan administration to negotiate the surrender of Taliban weapons in the hands of the remnants of the former regime's forces.
They said a number of delegation figures were killed and that a police chief, his deputy and members of a district council, were among those arrested. The head of the interim administration, Hamid Karzai, has also ordered a inquiry into the killings.
Earlier this week, Mr Rumsfeld said: "I do know that US soldiers have gone back into the area, I believe with Afghans, to try to determine the facts. I would hope that if, in the course of that, they discover that somebody was in fact killed who should not have been killed ... that American forces would express apologies. I can't say that I know that, but I would hope they would."
Asked about reports of compensation being paid, Mr Rumsfeld said: "I know nothing about that." But he admitted that Mr Karzai had raised the issue of compensation on his recent visit to Washington.
Mr Rumsfeld said the situation in Afghanistan was often complex and volatile, with Afghan fighters changing sides and those friendly to the United States meeting former Taliban fighters. "It is not a neat, clean, tidy situation," he said.
The apparent error underlines the extent to which US ground troops and air support are reliant on information received from Afghan allies who may wish to use American firepower in their local disputes.
In December, in Paktia province south of Kabul, a convoy of tribal elders on the way to the capital was attacked from the air with heavy casualties after a local warlord told the Americans that they were al-Qa'ida fighters.
Fear that the weakness of the central government in Kabul, the power of the warlords and deep ethnic divisions will lead to renewed fighting has persuaded many Afghans to ask for the British-led force of 3,200 peace-keeping troops in the capital to be expanded and stationed in other cities.
Geoff Hoon, Britain's Secretary of State for Defence, who was visiting Afghanistan yesterday, said Britain would help to build an Afghan army, but the international force would not be increased beyond the 5,000 limit agreed.
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