Mike Hanna, Al Jazeera's correspondent in Islamabad, said: "The staggering figure, in details released by the UN, shows that only about 2,000 people are actually in the refugee camps."
Around 20 per cent of the Pakistani displaced are in about 24 camps at the moment, John Holmes, the UN humanitarian chief, said.
Hanna said: "The rest are staying with family and with friends.
"This is obviously placing an immense amount of strain on the resources of the society as a whole increasing the magnitude of what is the biggest movement of people since the formation of Pakistan in 1947."
Risk of return
Earlier offensives had caused about 550,000 people to flee, though Ahmed said on Tuesday that 230,000 people had returned to Bajaur, a tribal region overrun by the Taliban and targeted in a lengthy military operation.
Speaking in Geneva, Ron Redmond, a spokesman for the UN refugee agency, said the massive displacement of people in such a short space of time "could go back to Rwanda" - a reference to the 1994 massacre of ethnic Tutsis by the majority Hutus in the African country.
The genocide displaced some two million people.
A UN statement had said earlier that 130,950 people had been registered in camps. It was not immediately possible to reconcile the difference.
"The situation is volatile and changing rapidly," Holmes said at the UN headquarters in New York.
Redmond said a lack of help for the displaced and the many thousands of families hosting them could cause more "political destabilisation" for the country.
The US has praised Pakistan's military operation in Swat and surrounding districts, which comes amid long-standing American pressure to root out al-Qaeda and Taliban hide-outs along the border with Afghanistan.