A British soldier has been killed and a further three injured in a suspected suicide bombing in Afghanistan.
The suicide attack which killed a UK soldier took place in Kabul
Four people were also killed in the attack on a Nato convoy in Kabul.
And a day of mourning has been declared at RAF Kinloss in Moray, Scotland, following the loss of one of the base's aircraft, which crashed in Afghanistan.
The Nimrod MR2 came down on Saturday, killing 12 air personnel from 120 Squadron, a Royal Marine and a soldier, all of whom have now been named.
An inquiry is under way, with a technical fault currently being blamed.
A Downing Street spokesman said Tony Blair viewed the latest death of a soldier with "sadness".
"It underlines again our debt of gratitude to the Army," he added.
When asked about calls for other nations to send more troops to Afghanistan, the spokesman replied: "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."
RAF Kinloss station commander Group Captain Chris Birks said all non-essential flights, not including search and rescue, had been grounded on Monday for a day of mourning as a result of the Nimrod loss.
Technical checks have been made on the fleet in Scotland and Afghanistan and a four-man board of inquiry is travelling to the Middle East to investigate the crash.
Foreign Office Minister Kim Howells rejected claims the UK's aircraft were worn out and more funds were needed.
Mr Howells, who is visiting the Afghan capital Kabul, said: "I've not heard that at all from our commanders, our generals out here, they seem very satisfied with the equipment they've got."
But Mr Howells did also suggest some of the other Nato countries with military deployment in Afghanistan ought to be "pulling their weight".
He said: "There are many nations out here who are part of this effort, but I think there has to be much more emphasis on ensuring that they are putting in the assets, the air cover, the soldiers on the ground, the transportation to ensure that those men and women on the frontline have got the support that they require."
Speaking later to BBC Radio Two, he said: "It's our job to make sure that everybody else is pulling their weight so that the British Army is not overstretched and our armed personnel are not being put unduly in a more dangerous position than the dangerous one they're in already.
"This is a very, very important fight that they're engaged in at the moment and this is a very critical moment in that fight."
As the Scottish base tried to come to terms with the tragedy, Wing Commander Martin Cannard, of 120 Squadron, said the victims were "great guys" and described their deaths as a "profound loss".
The 12 RAF personnel killed were named by the Ministry of Defence (MoD) as: Flight Lt Steven Johnson, Flt Lt Leigh Anthony Mitchelmore, Flt Lt Gareth Rodney Nicholas, Flt Lt Allan James Squires, Flt Lt Steven Swarbrick, Flt Sgt Gary Wayne Andrews, Flt Sgt Stephen Beattie, Flt Sgt Gerard Martin Bell and Flt Sgt Adrian Davies.
Also named were Sergeant Benjamin James Knight, Sgt John Joseph Langton and Sgt Gary Paul Quilliam.
The soldier who died was Lance Corporal Oliver Simon Dicketts from the Parachute Regiment and the Royal Marine was named as Joseph David Windall.
The plane had been supporting a major offensive, in which Nato said more than 200 Taleban have been killed.
Meanwhile, the new head of the British Army, Sir Richard Dannatt, has warned that his soldiers can only "just" cope with the demands placed on them by ministers.
BBC defence correspondent Paul Wood said: "The Taleban seem to be able to move at will around southern Afghanistan, and I think we're going to see this evolve more and more into an Iraq-like conflict, where these guerrillas do not confront NATO openly, they resort to tactics like suicide bombers."
The latest fatality brings the death toll of UK forces personnel in Afghanistan to 37 since the start of operations in November 2001.
There are 5,500 British troops in the country, helping to train Afghan security forces, facilitate reconstruction and provide security.
A special MoD helpline is available on 08457 800 900 for families concerned about relatives.