A US spokesman has again defended an air attack on Thursday near the city of Khost which was called after Australian special forces came under fire and which sparked the latest search operation.

Members of the Sabari tribe said 10 fighters killed in the bombing were Sabari engaged in a dispute with a neighbouring tribe and they had not fired on coalition forces.

Tribesmen told US officers at Khost airport that their fighters had been skirmishing with Balkhiel rivals over some trees near their villages 30 miles (48 km) north of the city when the bombing began.

But a US military spokesman, Major Bryan Hilferty, said on Sunday that he had "no reason" to believe the Sabaris' version of events.

"They were shooting heavy machine gun and mortars at us," he said, the ridge attacked by the AC-130 gunship was a "known al-Qaeda and Taleban area".

Sickness

About 1,000 coalition troops led by about 500 British marines are deployed in Paktia province to search for the militants.

Operation Condor, as the search is known, is taking place at heights of 6,000 to 8,000 feet where the air is thin.

Six marines have been evacuated from the operation, two with altitude sickness, one with a scorpion sting, and the others with acute sickness and diarrhoea.

Coalition forces in Afghanistan

11,000 troops from 17 countries including: US: 5,000 Canada: 2,200 Britain: 1,700 France, Australia, Denmark, Germany, Norway are also major contributors

Lieutenant Colonel Curry said on Sunday that another three British soldiers were due to return home after an outbreak of 'Winter Vomiting' disease at a field hospital at Bagram air base near Kabul.

At least 40 British personnel have been afflicted by the illness, which is characterised by one or two days of vomiting and diarrohea.

An infection control nurse has arrived from Britain to assess working practices at Bagram.

Spy plane lost

The British marines were sent to Paktia after another recent search operation in eastern Afghanistan failed to find any militants and soldiers were reported to be suffering form frustration at lack of combat.

Remaining militants are thought to have dispersed into small groups and blended in with local residents or fled across the border to neighbouring Pakistan.

The US air force has been supporting the search operation, using bases in both Afghanistan and Pakistan.

An unmanned spy plane crashed not far from the military base at Jacobabad in Pakistan this week, the latest of several such crashes in the Afghan campaign.

The BBC's Paul Adams, who is at Bagram air base, says the Condor operation could still prove a either a success or an embarrassment.