Defence Secretary Bob Ainsworth acknowledged this week that there was 'gloom and worry' about the British fatalities and admitted more lives would be lost.

'I do believe that we are making progress and I do believe that this is winnable, but it is not winnable in the short term,' he said.

News of the deaths came as the bodies of five other British soldiers killed in Afghanistan were flown back to RAF Lyneham, an air force base in the southwestern county of Wiltshire.

Relatives and hundreds of residents took part in a moving repatriation ceremony in the nearby town of Wootton Bassett Friday.

Meanwhile, Afghan and coalition troops captured six suspected militants, including two commanders of the Pakistan-based Haqqani network, a militant group associated with the Taliban, in two raids Thursday night in Khost province, the US military said in a statement.

It said one of the commanders was involved in smuggling suicide attackers, foreign fighters and weapons into neighbouring Afghanistan.

The raids took place at two compounds 10 kilometres southwest of Khost city after intelligence indicated militant activity at those locations, the statement said.

In Ghazni province, several militants were killed Thursday night after they opened fire on troops arriving to raid a compound in the Giro district, another US statement said. Some militants who fled the raid were also killed.

The statement did not detail exactly how many people were killed in the firefight, but four suspected extremists were detained in the raid.

Soldiers uncovered a weapons cache, including rocket-propelled grenade launchers and grenades, bomb-making equipment, one complete bomb and ammunition.

The US military said the aim of the operation was to disrupt the Taliban's operational and logistical support network for ambushes.

According to the statement, 'The Haqqani network remains one of the most lethal Taliban organisations operating out of Pakistan's federally administered tribal area.'