Attacks by the Taleban in Afghanistan surged last year, previously unpublished figures from allied military forces fighting insurgents show.
Statistics compiled by the multinational International Stabilisation Force in Afghanistan show attacks on international troops and the Afghan Government have gone up by between a fifth and a third.
But although admitting the figures show a significant rise, Nato insists the geographic extent of the violence remains limited.
"Seventy per cent of the incidents took place in just 10 per cent of the country, where no more than 6 per cent of the population live, and many have been initiated by our forces as we engage with the enemy," a source said.
"That is the same area as in 2006, which shows the insurgency is not spreading."
The figures, expected to be released shortly, will fuel the bitter dispute between Nato countries over military contributions.
Fierce criticism of European nations' efforts in Afghanistan has come from United States Defence Secretary Robert Gates.
And there has been a bad-tempered exchange between Berlin and Washington after the Germans received a "stern" letter from Gates asking for an increase in the soldiers they have sent to the north of Afghanistan.
Canada threatened to withdraw its troops, who have been fighting in the south and taking heavy casualties, if other nations did not do more.
In an attempt to cool the row, the US Secretary of State, Condoleezza Rice, is flying to London this week and a mini-summit of Nato defence ministers is also planned.
Nato sources argue that more troops are needed to fill gaps in the southwest in particular but say targeting resources on providing more training teams for the nascent Afghan Army would do more good than pouring in soldiers.
A particular frustration for the US is the restrictions imposed by national Governments on the deployment of their troops.
Germany, France, Italy and Spain - the latter two countries with troops in western Afghanistan - all agreed last year to send troops to the violent south, but only in extremis.
Since the agreement, no troops from those countries have been deployed.
General Carlos Branco, spokesman for Nato forces in Afghanistan, conceded that violence had increased in Afghanistan, but argued that suicide bombs reflected desperation by the Taleban.
"As an insurgency movement, the Taleban movement are a failure."
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