Six UK soldiers have been killed in southern Afghanistan when their vehicle was hit by an explosion on Tuesday.
Five from the 3rd Battalion the Yorkshire Regiment and one from the 1st Battalion The Duke of Lancaster’s Regiment had been on patrol. Their families have been told.
It is the biggest single loss of UK life at one time in Afghanistan since a Nimrod crash killed 14 in 2006.
The number of British military deaths in Afghanistan since 2001 is now 404.
Prime Minister David Cameron said it was a “desperately sad day for our country”.
“Every death and every injury reminds us of the human cost paid by our armed forces to keep our country safe,” he said, at the start of Prime Ministers’ Questions.
In a statement from the MoD, Lt Col Gordon Mackenzie, spokesman for Task Force Helmand, said the six soldiers were on a security patrol in a Warrior armoured fighting vehicle when it was caught in an explosion just over the Helmand border in Kandahar province.
They had been travelling as part of a two Warrior patrol when the vehicle was hit at a junction where a road travelling east from Gereshk meets another heading north to Lashkar Gah, the MoD said.
It is understood British forces believe the explosion was caused by either a roadside bomb laid by insurgents or a legacy mine, left over from the Soviet era.
The BBC’s Orla Guerin, in the Afghan capital Kabul, said there must have been a “massive explosion” to damage such a robust and heavily protected vehicle.
The area, she said, was sparsely populated and particularly unstable, according to Afghan officials, and insurgents were known to have planted roadside bombs there.
Meanwhile, the BBC’s defence correspondent, Caroline Wyatt, said the six soldiers had been in the country for less than a month, having flown out of the UK on Valentine’s Day.
She added that the ongoing operation to recover the bodies would have been slowed down as rescuers would have faced the risk of being injured themselves by further bombs.
News emerged earlier on Wednesday that the six were missing, presumed dead. It is understood the MoD has not formally identified the soldiers yet, but they are dead.
Most UK troops are expected to be withdrawn from Afghanistan by the end of 2014, when 13 years of combat operations in the country are set to cease.
Defence Secretary Philip Hammond said the timetable for withdrawal remained on track despite this “cowardly attack”.
“This will not shake our resolve to see through the mission – I believe we owe that to all the brave men and women who have sacrificed their lives and put themselves at risk over the last few years,” he told the BBC.
In the Commons, Mr Cameron told MPs “every possible support” had to be given to a political settlement in Afghanistan and a clear message had to be sent to the Taliban that – whether UK troops or Afghan troops were there – they “will not win on the battlefield – they never win on the battlefield”.
Mr Cameron said he had spoken to the UK’s leading military officers, who had stressed the commitment of troops to “getting the job done”.
He also said he would discuss the Afghanistan situation with President Barack Obama on his visit to the US next week to ensure they were “in lock step” about the importance of training up the Afghan army and police, and making sure all Nato partners had a properly co-ordinated process for transition.
Chief of Defence Staff General Sir David Richards said he was “deeply saddened” by the news.
“The courage, fortitude and determination of those servicemen and women currently in Helmand is inspirational,” he said.
Shadow defence secretary Jim Murphy said it was a “terrible tragedy which will bring profound loss to six families and real hurt to the whole country”.
The Archbishop of York John Sentamu said his heart went out to those affected, and we owed a debt of gratitude to our “brave soldiers”.