Thousands of mourners bowed their heads in tribute Friday to the passing coffins of British soldiers killed in a new offensive in Afghanistan, where the climbing toll has created doubts in Britain about the human cost of the war.

News of 15 battlefield deaths in 10 days has many Britons rethinking the country's commitment to a conflict that seems no closer to a successful conclusion than when troops first arrived seven years ago.

A Ministry of Defense spokeswoman said a total of eight deaths were announced Friday, making it one of the darkest days of the war. She spoke on condition of anonymity in line with department policy.

"The casualties should fix peoples' minds on the fact that we've let the soldiers down," said Adam Holloway, an opposition Conservative Party lawmaker who sits on Parliament's defense committee. "The death toll means we should do it properly or we shouldn't do it at all."

Holloway, a frequent visitor to Afghanistan, said Britain has never had the troop strength needed to hold ground there and has failed to provide the promised security or reconstruction, leading many Afghans to believe the Taliban militants will outlast Western forces.

"We're in a mess," he said.

He cautioned that there is still no widespread public revolt against the government's war policy. He said his constituents do not seem extremely worried about the troubled Afghan campaign, despite the increasing casualties.

But some communities are grieving. Schoolchildren, businessmen and army veterans stood side by side in Wootton Bassett, a small market town about 85 miles (135 km) west of London, as the bodies of five soldiers killed between Saturday and Tuesday were driven through the crowds after being flown to a nearby air base.

Wootton Bassett's mayor, Steve Bucknell, said it was becoming increasingly hard to accept the rising number of British casualties.

"We keep on asking ourselves how many more? Each time we pray it's the last one, knowing it probably isn't going to be," Bucknell said.

It has become traditional for the residents to line the streets when hearses carrying soldiers' coffins pass through the town on the sad trip from a military airport to a cemetery.

The casualty count mounted Friday night when officials said five soldiers were killed in two separate explosions while on patrol. Earlier in the evening, the Ministry of Defense announced that a soldier from the 2nd Royal Tank Regiment had been killed in an explosion. Two other deaths were announced earlier in the day.

The names of the dead soldiers are likely to be released in the next 24 hours.

The deaths have come in volatile southern Helmand province in the past nine days amid a new offensive to uproot Taliban fighters. Seven years after British forces first deployed to Afghanistan — and after the loss of 185 troops — ex-military chiefs are criticizing tactics and equipment while members of the public wonder about the benefit of taking part in the conflict.

Defense Secretary Bob Ainsworth and Prime Minister Gordon Brown claim that Britain's role in Afghanistan is crucial to root out extremist terrorists who could potentially attack the United Kingdom, and to prevent a tide of Afghan heroin from reaching British streets.

Brown said Friday that the war is vital to Britain's security.

"There is a chain of terror that runs from the mountains and towns of Afghanistan to the streets of Britain," he told reporters at the G-8 summit in L'Aquila, Italy. "Having talked to President Obama and the rest of the world leaders, there is a recognition that this is a task the world has got to accept together and this is a task we have got to fulfill."

Michael Clarke, head of London-based military think tank the Royal United Services Institute, said public concern is mounting and urged politicians to be more honest about Britain's initial reasons for joining the 2001 invasion.

"What they won't really say is that it's about the credibility of the NATO alliance, and our military relationship with the United States," Clarke said.

Some critics say that Britain should either withdraw from the mission, or that troops must be provided with better equipment, including more helicopters. Britain, the United States and Canada have long complained that they have engaged in heavy fighting in Afghanistan while some European nations have shied away from combat roles.

Tony Philippson, whose son James was killed in Afghanistan in 2006, said the public remained skeptical about whether foreign troops will ever be able to suppress the Taliban and bring peace to the country.

"I've always felt it was a risky business and I think it's still on a knife edge about whether they can succeed," Philippson told the BBC.

Gen. Charles Guthrie, the head of Britain's military between 1997 and 2001, said he believes British soldiers have died as a direct result of a shortage of helicopters for troops in Afghanistan. British troops are suffering heavy casualties from roadside bombs, and a lack of helicopters mean soldiers must make more journey across Helmand by road.

"If there had been more, it is very likely fewer soldiers would have been killed by roadside bombs," Guthrie — a longtime advocate of higher defense spending — was quoted as telling the Daily Mail newspaper.

Britain's defense ministry declined to disclose how many helicopters Britain has in Afghanistan on security grounds, but said additional aircraft are being sent to support the mission.

The ministry said that the two latest casualties died in separate incidents Thursday. The bloodshed has intensified as Afghans prepare for elections planned for next month.