Two more Nato soldiers were today killed in Afghanistan as the UK and US said its allies must deploy more troops or face losing credibility.

The soldiers, whose nationalities have not yet been released, were killed after their patrol was struck by an improvised bomb in a province near Kabul, according to a statement from Nato.

An interpreter was also wounded when a Nato-led International Security Assistance Force (Isaf) combat patrol hit an explosive device in Logar province. Most of the troops in Logar are US nationals, who make up about half of the 122 foreign soldiers now killed in action in Afghanistan this year.

The attack occurred as George Bush and Tony Blair pressed members of the alliance to deploy more troops to Afghanistan to help combat a strengthening insurgency from the Taleban, which has led to unexpectedly high casualties.

This year’s attacks have claimed the lives of some 3,700 people – four times more than last year.

Today’s incident came just hours after a suicide blast in the western city of Herat, which killed a policeman, and another in the southern province of Kandahar, which wounded an Isaf soldier. Yesterday, two Canadian soldiers were killed in a suicide car bombing in Kandahar in the third suicide bombing in the country in three days.

Major Luke Knittig, an Isaf spokesman, said the recent increase in Taleban-instigated violence was designed to "shake the will" of Nato leaders, who have gathered in Riga, Latvia ahead of a summit focused on Afghanistan’s deteriorating security situation and the perilous mission being undertaken.

Speaking in Riga, George Bush earlier urged fellow members to send in more troops, berating nations which have imposed conditions on the use of their forces, such as placing geographical restrictions on where troops can be sent, or refusing to let them to fight at night or in winter conditions.

"For Nato to succeed, its commanders must have the resources and flexibility they need to do their jobs," Mr Bush said in the Latvian capital Riga.

He challenged the 26-member alliance to show the same support for troops in Afghanistan as they had shown for the US in the wake of the 9/11 attacks in 2001.

"This alliance was founded on a clear principle: an attack on one is an attack on all. That principle holds true whether the attack is on our home soil or on our forces deployed on a Nato mission abroad," he said.

The strength of the insurgency, at its worst in the south and east of Afghanistan, sparked a call in September by military commander General James Jones for 2,500 reinforcements, to support the 32,000-strong Nato force.

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