Explainer: Why Casualties Are Up

The war in Afghanistan is entering a crucial stage as Taliban leaders resort to "terrorist" tactics with the help of foreign fighters exposing British troops to greater danger, analysts said yesterday .

"Its been a bad couple of weeks for the British mission in Afghanistan, not because the strategy isn't working - it demonstrably is - but because the human costs of a successful strategy are now evident," Michael Clarke, director of the Royal United Services Institute, said. "The Taliban have been reduced to a band of opportunist terrorists. This makes them politically less relevant to Afghanistan's future but more lethal to individual British service personnel."

Paul Cornish, head of Chatham House's international security programme, described an "ever-widening disjunction" between the war-fighting and "hearts-and-minds" missions of British forces. There was consensus, too, that the more vulnerable British soldiers were to attacks from roadside mines and suicide bombers, the more difficult it was for them to carry out the reconstruction operations Gordon Brown says are now a priority.

Defence officials say that the Taliban commanders' shift in tactics was not what they expected but suggested they were on the back foot. "Their use of foreign fighters indicates that the Taliban's normal recruitment base has been undermined," an official said, referring to Uzbeks, Chechens, and Arabs believed to be joining the insurgency.

The army has been trying to develop electronic countermeasures to protect Land Rovers and armored vehicles . There is evidence that roadside bombs laid by insurgents in Iraq have been made, or at least designed, in Iran. Officials believe that elements in Iran - perhaps the Revolutionary Guards - are also supplying the Taliban with the weapons.