US forces killed in Afghanistan

US bombers have been targeting al-Qaeda positions

The Americans have suffered their highest casualties in combat since the war in Afghanistan began, with at least eight soldiers killed during operations in the east of the country.

I am just as determined now as I was a week ago or three months ago to fulfil this mission and that is to make sure our country is safe

President Bush

General Tommy Franks, head of the US Central Command, said about 40 Americans had also been wounded as part of Operation Anaconda, which is seeking to root out Taleban and al-Qaeda forces from mountains south of Gardez in Paktia province.

President George W Bush said he was saddened by the loss of life but remained determined to rout the al-Qaeda network.

"History has called us to defend freedom," he said after a meeting with teachers in the state of Minnesota.

The Chairman of the Joint Chiefs of Staff, General Richard Myers, said the war was entering a difficult and dangerous phase, with US casualties likely following the insertion of large numbers of troops on the ground.

Small arms fire

Eight or nine US servicemen were killed when their aircraft were hit by enemy fire, General Franks said.

In one incident, an army Chinook helicopter airlifting US troops in the Gardez area was hit by small arms fire and then attacked after landing.

Another soldier is thought to have died when he fell out of a second helicopter which was hit but managed to get away.

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Ten US soldiers were also wounded in the attack, which happened at about 2230 EST (0330 GMT on Monday).

The helicopter that was shot down was a MH-47 special operations Chinook helicopter, thought to be carrying up to 24 troops, which was taking part in operations against suspected al-Qaeda and Taleban fighters.

	First delivered: 1994 Speed: 238 km/h Capacity: 33 troops Cargo: 12,210 kg  Chinook: Versatile warhorse

General Franks said that 100-200 enemy fighters had also been killed.

Defence Secretary Donald Rumsfeld stressed that the military operation in Afghanistan would continue until the al-Qaeda presence was eliminated.

He said substantial pockets of dangerous and determined resistance remained.

Heavy battle

The helicopters are the first US aircraft shot down in action since the anti-terror war began in Afghanistan last October.

Afghan fighters form about half the assault force

The incident comes as the largest coalition force assembled so far in Afghanistan - about 1,500 in total - remains heavily engaged in ground battles with the militants.

An Afghan commander on the ground said his forces had captured a strategically important ridge and expected the operation to be over in days.

Troops from Australia, Canada, Denmark, France, Germany and Norway are also involved alongside US army and special forces and Afghan fighters.

French aircraft were used in the campaign for the first time.

High-altitude battle

US heavy bombers and AC-130 gunships have been targeting the militants' vehicles, mortar positions and caves.

Warning: "Surrender militants or die"

US military officials said there had been "intense" clashes since Saturday as the US-led force encountered artillery, mortar and heavy machine-gun fire.

US planes are currently using new "thermobaric" laser-guided bombs in an effort to flush out the militants in the mountains.

The 2,000-pound (907-kg) laser-guided weapons are filled with a special explosive mixture that creates a high-pressure blast, driving all of the oxygen out of a cave and potentially choking those inside.