"Even in Darfur it took a considerable amount of time for the [number of internally displaced people] to swell up."
Bodies in streets
The announcement by the Pakistani military covers the towns of Mingora, Kamabar and Kabal.
"It is going to be very difficult to separate the Taliban from the ordinary people," Hyder said.
"The Taliban also know they are fighting a losing battle and that without the support of the people they would not stand a chance."
Tens of thousands of Pakistani civilians in the Swat valley have found themselves trapped amid worsening fighting between government forces and the Taliban.
Bodies were reported to be lying in roads, homes reduced to ruins and people left cowering with no means of escape after the military imposed curfews across the region amid the fighting.
"Anger is growing that the government did not give the citizens adequate warning to escape," Hyder reported.
"Many people are saying their government has abandoned them ... what is unfolding here is the tip of the iceberg, the worst is yet to come."
Hundreds of thousands of civilians have already fled the fighting, many ending up in refugee camps.
Hyder said there was little government help available to those who had fled.
"We went to an IDP (internally displaced persons) camp today ... there were no signs of officials from the provincial government," he said.
"There has been a lot of talk, but they have not done anything. There is, understandably, reasonable justification for [the civilians'] anger at the government."
Major-General Athar Abbas, the Pakistani army's chief spokesman, said that government forces were deployed across the Swat valley.
"More than half of Mingora [the main town in Swat valley] is under the control of the militants ... to establish some sort of security control over the area, the curfew was imposed," he told Al Jazeera.
The UN refugee agency (UNHCR) and Pakistani officials has said that about half a million people have been displaced in the last few days since the Pakistani government launched a major offensive against the Taliban.
Another 500,000 people were also reportedly displaced amid violence in the region over the last few months.
Antonia Paradela, a spokeswoman for Unicef, the UN children's rights organisation, said aid agencies would need more funding to cope with the influx of refugees.
"We need urgently more funds ... Unicef needs at least $10m to continue helping the previous group of displaced families, which is more than half a million people," she told Al Jazeera.
"We're talking now more than 200,000 - and more [are] on the move."
The crisis has been intensified by other aid groups halting their work in the face of the fighting.
"A week ago we had to suspend our services due to growing insecurity which has left large numbers of the population without the necessary medical care at a time of dire crisis," Chris Lockyear, the Doctors without Borders' head of mission in Pakistan, told Al Jazeera.
"We would like to go back ... but at the moment we are finding the security is not even allowing us to evacuate patients to safer areas for treatment," he said.
The fighting has prompted the abandonment of a peace deal, agreed in February, between the government and the Taliban.
The deal had been criticised both at home and abroad and its critics, especially in the US, have welcomed the government's offensive.
Asif Ali Zardari, Pakistan's president, pledged an all-out war against Taliban fighters during a visit to Washington for talks with Barack Obama, the US president, and Hamid Karzai, the Afghan president.
"This is an offensive - this is war. If they kill our soldiers, then we do the same," Zardari told America's PBS public television.
Obama pledged a "lasting commitment" to both Pakistan and Afghanistan, where the US is fighting Taliban forces.
Up to 15,000 members of Pakistan's security forces have been deployed in Swat.