BBC correspondent Ian Pannell, embedded with British troops in Helmand province, describes the impact on morale
A third British soldier has been killed in Afghanistan, hours after the deaths of two soldiers in Helmand, the Ministry of Defence has said.
The death takes the number killed in Afghanistan since 2001 to 179 - the same number as killed in the Iraq war.
The soldier, from the 2nd Royal Tank Regiment, died in the country's south. His next of kin have been informed.
Ten British soldiers have now died in Afghanistan this month, including the two in separate attacks on Thursday.
The serviceman who died on Friday was killed near Nad Ali, Helmand province.
Lt Col Nick Richardson, spokesman for Task Force Helmand, said: "The loss of this brave Tankie has hit us all deeply. We grieve for him at this very sad time.
"Our thoughts and prayers are with his family, friends and colleagues who feel the greatest loss. His loss has not been in vain."
One of the two soldiers to die on Thursday was from 4th Battalion The Rifles. He was killed in a blast while on foot patrol near Nad Ali.
The second, from Princess of Wales's Royal Regiment, attached to 1st Battalion Welsh Guards, was killed during an engagement with insurgent forces near Lashkar Gah on Thursday evening.
Prime Minister Gordon Brown responded to the news of the first two deaths from Italy, where he is attending the G8 summit.
"This is a very hard summer, it's not over but it's vital that the international community sees through its commitment [to Afghanistan]," he said.
"There's a recognition that this is a task that the world has got to accept together.
"We must and we will do everything we can to support our forces as they put their lives on the line."
Defence Secretary Bob Ainsworth insisted that the conflict was "winnable" but warned that there would be no early end to the fighting.
BRITISH FATALITIES IN AFGHANISTAN MARCH 2006 - JULY 2009
September 2006: Highest monthly toll with 19 dead including 14 killed when a RAF Nimrod crashes in Afghanistan.
June 2008: British death toll reaches 100 with the death of Pte Daniel Gamble, above. Among the 13 fatalities in June is the first British female soldier.
May 2009: Surge in casualties as Taliban use powerful Improvised Explosive Devices to attack British forces.
Speaking earlier on Friday Lt Col Richardson had said their deaths "were not in vain".
Kelly Gore, from Bridgend, south Wales, lost her partner L/Sgt Tobie Fasfous, when he was killed by an explosion in Helmand in April.
On Sunday she heard their friend L/Cpl Dane Elson had also been killed.
Hearing about so many deaths over a few days had been particularly difficult, she told the BBC.
Kelly Gore's partner died in Afghanistan in April
"It's just awful. It just takes you back to that day, that horrible day, the devastation it causes for families is unbelievable.
"Your whole world falls apart in seconds."
She said although she backed the soldiers "one thousand per cent" she had questioned why Tobie and others went to Afghanistan.
"I just hope something good does come out of this. Then the boys did good. They died for a reason."
British forces are engaged in a major offensive in Helmand province, in the south of the country, and have been joined by about 4,000 US and 650 Afghan troops.
The joint campaign is designed to drive the Taliban out of the region and make it safe for presidential elections due next month.
The bodies of five soldiers killed in Afghanistan over the past week were returned to the UK on Friday.
The aircraft carrying their coffins arrived at RAF Lyneham, in Wiltshire, for a repatriation ceremony.
HAVE YOUR SAY
The government is not doing enough for our military. We need a massive surge of British troops to take more of the fight to the Taliban
James McCartney, St Austell
After the ceremony, hearses carrying the coffins passed through nearby Wootton Bassett, which was lined with hundreds of mourners.
The former UK ambassador to the United Nations, Sir Jeremy Greenstock, has told the BBC he does not think the operation in Afghanistan was well-enough resourced.
He said: "We don't have enough troops in the Army to run these sorts of operations any more, we've cut down too far."
But he said: "We want to see an Afghanistan that doesn't threaten us, therefore we do have dogs in this fight."