A fresh flood of refugees poured out of Pakistan's Swat valley on Friday as authorities temporarily relaxed a curfew ahead of a looming ground onslaught against the Taliban.
The UN refugee agency said more than 834,000 civilians had been registered since May 2, adding to another 555,000 civilians who fled escalating violence last year.
But not all the displaced people have got themselves registered, and a minister in the North-West Frontier Province (NWFP), where Swat is situated, estimated the fresh displacements at 1.5 million, with nearly a million more still stuck in their homes.
Pakistan's Prime Minister Yousuf Raza Gilani called for "winning the hearts and minds" of the uprooted people, saying "It will be very unfortunate if we win militarily but lose publicly".
Security forces temporarily lifted the curfew in parts of Swat and the nearby districts of Lower Dir and Buner from 6 am to 2 pm (0000 to 0800 GMT) on Friday to allow the marooned population to flee the intense fighting between the military and the Taliban militants.
Nearly 15,000 troops with air and artillery support are trying to eliminate up to 5,000 hardcore insurgents. But so far urban warfare has been avoided to prevent collateral damage.
Fresh battles are expected in Mingora, Swat's main town, where tens of thousands of people are still believed to be stranded.
The army said the offensive was "progressing well" and soldiers had established a foothold in Peuchar, a key militant bastion where airborne troops were dropped this week for search-and-destroy missions.
Officials said more than 800 militants and 43 soldiers had been killed in the offensive. However, the toll could not be verified independently.
The operation was launched in late April when a controversial peace agreement collapsed after the emboldened militants overran Swat's adjoining district of Buner, located just 100 km north-west of the capital, Islamabad.
The advance triggered a consensus at home and abroad that decisive action was inevitable against the "existential threat".
But analysts fear the broad support for the military assault could change in case of high numbers of civilian casualties or if the suffering of the displaced people was not duly addressed.
UN High Commissioner for Refugees Antonio Guterres visited one of the makeshift refugee camps on Thursday and sought international support for the displaced people who he said could contribute to destabilisation if not helped out.
According to the military there are no reports of non-combatants getting killed in its actions, but the army blamed the Taliban for causing civilian casualties by planting roadside bombs and targeting fleeing residents.
Officials described the mass exodus as the largest since the country gained independence in 1947.
The refugees, who are used to a cooler climate, are bracing for extremely hot weather as temperatures have already soared above 40 degrees Celsius in areas hosting the temporary shelters.
Fistfights between the displaced people have also been reported during distribution of food and other relief supplies.
Health authorities are concerned about unhygienic conditions at the camps, with reports of a diarrhoea breakout affecting around 150 women and children at one camp.