In a black day for the UK military, two British troops were killed near Basra in Iraq and a third soldier attached to the Nato mission in Afghanistan died in a suicide bomb attack on his convoy in Kabul.
As casualties mounted, the army's most senior officer warned that troops were fighting at the limit of their capacity.
General Sir Richard Dannatt, the Chief of General Staff, said the Army can only just cope with the demands being placed on it by the Government, and warned that the UK had taken on "more than its share" of military work in Afghanistan.
A further three soldiers were injured in today's incidents. In Iraq, a further two British troops were hurt, one of them seriously, when their convoy came under attack from a roadside bomb and small-arms fire near the town of al-Dayr, north of Basra, at 1pm local time (1000 BST).
Both the injured soldiers were taken by helicopter for emergency medical care at a British field hospital at Shaibah Logistics Base.
In Kabul, a second Briton was very seriously injured when the suicide bomber crashed his a four-wheel drive vehicle into the convoy on the road from the capital to Jalalabad at around 10.30am local time.
The MoD said in a statement: "We can confirm that a UK military convoy has been attacked by a suspected suicide bomber in Kabul at approximately 10.30 local time this morning.
"Sadly, one UK soldier has been killed and another very seriously injured as a result of this attack. The injured soldier has been evacuated to a military medical facility for treatment. No further details of the incident will be released until next of kin have been informed."
Concerns over the demands being placed on troops were fuelled by an interview in which General Dannatt warned that the Army was being forced to "meet challenges on the hoof".
Speaking to The Guardian about the scale of Army commitments in Afghanistan, Iraq and elsewhere, General Dannatt warned: "We are running hot, certainly running hot. Can we cope? I pause. I say ‘Just’."
The general - who took over the Army’s top job last week and gave his interview before news emerged of today's casualties - called for a "national debate" over whether the UK’s annual £30 billion spending on defence was sufficient.
Asked whether other Nato countries should contribute more to joint operations, he said the UK was doing "more than its share of what is required in Afghanistan".
Kim Howells, the Foreign Office minister who is currently visiting Afghanistan, also urged Britain’s Nato allies to make a bigger contribution to the current operation to bring security to the Taliban-dominated south of the country.
Speaking to BBC Radio 4’s Today programme, Dr Howells denied the Army was overstretched and said commanders on the ground were "very confident that they have got the resources to do the job that they are there to do".
But he added: "The job could be done much quickly and, I think, much more safely if it’s clear that all of the Nato members involved in this are pulling their weight."
He went on: "The burden of actual fighting is probably being carried disproportionately by the Americans, the British, the Dutch and some of the smaller Nato nations, and I think it is very important that everybody understands that."
Tony Blair’s official spokesman said it was sometimes better for discussions on contributions to international operations to be conducted behind the scenes.
"Countries, as we have seen in the Middle East, sometimes take time to reach these kind of decisions, but what is happening in Afghanistan underlines the reasons why we need to support the democratic government of Afghanistan and its developing army," he said.
He denied Britain had extended its planned role in Afghanistan, saying: "What we have done is fulfilled the role that was envisaged when we said we would take over the leadership of the Allied Rapid Reaction Corps."
Gerald Howarth, the Shadow Defence Minister, backed General Dannatt’s call for a national debate on military spending.
"The fact is that this prime minister has engaged in five military operations since he became Prime Minister," Mr Howarth told BBC Radio 4’s World at One.
"He shows no reluctance to commit British forces around the world but his Chancellor, Gordon Brown, will not commit the necessary funds to ensure that our men have the latest and best equipment."
Michael Moore, the Liberal Democrat Foreign Affairs Spokesman, said: "With the head of the Army saying our forces can only ’just’ cope, we urgently need to know whether British troops have the manpower, support and equipment they need.
"Dr Howells’s concession that British forces are having to wage war on terrorists means that ministers must urgently clarify whether the mission (in Afghanistan) has changed and what exactly our troops are being asked to do.
"We need achievable goals and the military capabilities to achieve them. And we need a strategy that addresses not only security threats but the full spectrum of political and reconstruction needs."
On a bad day for Nato's Afghan mission, its warplanes accidentally killed a Canadian soldier and wounded several others in a "friendly fire" incident near Kandahar. The incident occurred during a Nato-led operation against the Taleban in the Panjawyi district of Kandahar after ground troops requested air support, Nato said.
"Two Isaf (Nato's International Security Assistance Force) aircraft provided the support but regrettably engaged friendly forces during a strafing run, using cannons," it said in a statement, adding that there were "multiple casualties."
On Sunday, four Canadian soldiers were killed and seven wounded in the same operation, dubbed Medusa, to drive a large group of Taleban militants from Panjwayi, which lies to the West of Kandahar. Nato reported that more than 200 Taleban fighters had died in the first two days of the operation, which began on Saturday.
Some 117 British troops have now died in Iraq since the outbreak of hostilities in 2003. Today's death near Kandahar bring to 37 the number of UK personnel killed in Afghanistan since operations began in 2001, following the loss of 14 troops when an RAF Nimrod crashed near Kandahar on Saturday.
The plane, which had been conducting aerial reconnaissance, came down while trying to make an emergency landing after suffering a tail fire that damaged its electrical systems.
Jack McConnell, Scotland’s First Minister, today paid tribute to the 14 victims, most of them based at RAF Kinloss in Moray, northeast Scotland, where a day of mourning was held today with all non-essential flights grounded.
Mr McConnell said: "It will be a very difficult time, not only for the family of those involved but for the entire community. I know that they will support each other through this tragic period.
"I would like to pay tribute to the bravery of those killed and of those who continue to serve in our Armed Forces throughout the world."
A four-man board of inquiry is now on its way to the Middle East to begin its investigation into the crash, which was the biggest single loss of life suffered by British forces in the War on Terror.
