More than half a million civilians have already fled the region since the operation was launched on June 15, said an official with the disaster management agency.
Prime Minister Nawaz Sharif ordered the military to eliminate terrorists hiding in their so-called safe heavens after frustrating efforts to engage Taliban insurgents in a peace process.
The military said nearly 400 fighters have been killed in the two-week campaign but the figure could not be verified independently due the inaccessibility of the area.
People fleeing the area have told Pakistani television channels civilians were also being killed in airstrikes and that most militants escaped to southern Afghanistan even before the operation started.
The army denied this, saying their troops had surrounded the militants.
There is growing skepticism in Pakistan over the effectiveness of the offensive in ending years of violence that has claimed around 50,000 lives in a decade.