Pakistani civilians have been caught in the crossfire
Thousands of people have fled Pakistan's violence-hit Swat district after the army briefly lifted a curfew.
Local residents trapped by fighting between troops and Taleban militants were given a few hours to leave.
The army is trying to reverse militant advances in the area, in what the prime minister has called a "fight for the survival of the country".
It says it has killed between 180-200 militants in the last 24 hours in Swat and other areas.
Between 50 and 60 militants were killed in Swat on Sunday and about 140 bodies had been found in neighbouring Shangla district, the military said in a statement.
Clashes were also reported in the nearby districts of Dir and Buner.
In Swat, explosive devices planted by the militants in roads and militant mortar fire were causing civilian casualties, the military said.
Due to the intensity of the fighting and the cutting of phone networks, it is difficult to get independent information on the fighting, correspondents say.
'Relying on God'
Early on Sunday, the military lifted a curfew in Swat to allow residents trapped by the fighting to get out.
Residents in the main town of Mingora and the nearby towns of Kambar and Raheemabad began leaving at 0600 (0100 GMT).
Syed Shoaib Hasan
BBC News, Islamabad
The army has spent the last two days locating and destroying militant camps in the rural regions.
A major ground offensive now appears to be on the horizon to secure the seat of government in Swat.
The Taleban have entrenched themselves in fortified position in and around Mingora. The army is likely to use aircraft and artillery to soften up these targets before sending in ground troops.
But even then, the fighting on the ground is expected to be bloody and long drawn-out.
As dawn broke in Mingora, thousands of civilians were setting out. A local journalist described the event as something out of Doomsday, reports the BBC's Syed Shoaib Hasan in Islamabad.
Men, women, children and the elderly were seen moving along the road that leads out of the region.
The lucky ones were able to get some sort of transport, ranging from a local bus to a donkey cart.
But many plodded down the road on foot carrying what little they could gather, our reporter said.
"We are going out only with our clothes and a few things to eat on the long journey," Rehmat Alam, a 40-year-old medical technician, told the Associated Press news agency.
"We just got out relying on God because there is no one else to help us."
The curfew has now been re-imposed. Analysts say the decision to lift it for most of the day is a sign that the army offensive is likely to intensify in the coming days.
Ariane Rummery from the UN refugee agency on the 'humanitarian challenge'
Pakistan's government signed a peace agreement with the Swat Taleban in February, allowing Sharia law there, a move sharply criticised by Washington.
The militants then moved towards the capital, Islamabad, causing further alarm.
Up to 15,000 troops have now been deployed in the Swat valley and neighbouring areas to take on up to 5,000 militants. The military has said it intends to "eliminate" the Taleban fighters.
Prime Minister Yusuf Raza Gilani on Saturday called the conflict "a guerrilla war".
"This is our own war. This is war for the survival of the country," Reuters news agency quoted him as saying.
The fighting has already displaced some 200,000 people, while a further 300,000 are estimated to be on the move or poised to flee, the UN says.
On Saturday the government said that refugee camps would be set up in Peshawar, the capital of North West Frontier Province, and to the north-east in Naushara.
Footage on local television showed people at one camp desperately looting UN supplies, including blankets and cooking oil.
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