The needs of civilians who have fled are overwhelming the authorities
Pakistan's army has temporarily lifted a curfew in large parts of the Swat valley to allow civilians to flee the intense fighting against the Taleban.
The curfew is being suspended for eight hours during the day, officials say.
Prime Minister Yousuf Raza Gilani has vowed the army would successfully clear the valley of militants who have largely controlled the area for months.
The UN says more than 800,000 people have been displaced by fighting in the region in recent months.
Many tens of thousands are living in camps in the area around the city of Mardan. Thousands more arrived after the curfew was eased at the weekend.
A further influx is expected on Friday as it is lifted in parts of the Swat valley from 0600 to 1400 (0100-0900GMT).
About 150,000 civilians are trapped in the main city, Mingora, with gas, electricity and food increasingly scarce, the BBC's Barbara Plett in Islamabad says.
Residents told the AFP news agency that Taleban holding the city had mined roads and dug trenches around it.
Up to 15,000 troops have now been deployed in the Swat valley and neighbouring areas to take on up to 5,000 militants.
Military operations including artillery shelling of suspected militant hideouts in Swat and the neighbouring district of Lower Dir killed about 124 militants and left nine soldiers dead in the 24 hours before the curfew was relaxed, the army said.
But a Taleban spokesman, Muslim Khan, says the militants have killed at least 37 soldiers in fighting since Wednesday, with just three of their fighters killed.
The BBC's M Ilyas Khan in Islamabad says independent confirmation of these claims is difficult as the phone system across Swat is down and tens of thousands of mobile phones have gone dead because of a lack of electricity.
As the operation stepped up on Thursday, Pakistan's army chief Gen Ashfaq Kayani visited troops on the frontlines - reportedly for the first time since the bombardment began.
He is now due to brief MPs behind closed doors on the ongoing operation.
Analysts in Pakistan believe the Taleban have been losing public sympathy since a video emerged in March showing militants flog a girl in Swat.
Statements by Maulana Sufi Mohammad, who brokered the failed peace deal between the government and Swat militants, have also caused political alarm across the country.
The fighting is Swat has escalated this after weeks of low-level conflict between troops and militants.
The army opened a new front earlier this week by airlifting troops to Peochar, which is about 65km (40 miles) north-west of Mingora.
The army says it has made advances in the Peochar area, but militants say they have been successfully resisting, inflicting heavy casualties on government troops.
UN High Commissioner for Refugees Antonio Guterres has warned that the plight of displaced people could spark further conflict.
"If you are not able to cope with the challenges posed by overwhelming displaced... this population will become a huge factor of de-stabilisation," Mr Guterres said after visiting a camp for people displaced by the fighting.
The UN has called for a massive and urgent injection of emergency humanitarian aid.
The Pakistani government began its offensive in the Swat valley in late April.
In February, it had signed a peace agreement with the Taleban there, allowing Sharia law to be enforced, in a move sharply criticised by Washington.
But the militants then expanded into neighbouring districts, prompting the government to abandon the peace deal.
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