The hundreds of thousands of refugees now pouring out of the mountainous Swat are used to cooler climes and clean air - but they are running straight into the perilous embrace of Pakistan's sweltering summer. Aid officials warn that the soaring temperatures are already taking a merciless toll on the refugees. Children in particular are falling victim to heat stroke and dehydration. And in such cramped conditions and with poor sanitation and little water, the heat makes it more likely that diseases will spread.

Already overstretched by the 900,000 people estimated by the UN to have fled from Swat and the surrounding areas of Buner and Lower Dir in the past three weeks, officials are bracing themselves for more. Yesterday thousands of refugees streamed from Swat after the military temporarily lifted a curfew, allowing residents to escape so that it can engage the militants in "street-to-street fighting".