ISLAMABAD - A recent Pakistani military offensive against Taliban fighters in the northwest has killed more than 1,000 suspected insurgents, a top official said Sunday after visiting a relief camp hosting thousands of people displaced by the battle.

Interior Minister Rehman Malik gave no time frame for how much longer the operation would proceed, except that it "will continue till last Taliban are flushed out."

It was not possible to independently verify the figures provided by Malik.

The areas covered by the operation, including the northwest's Swat Valley, are too dangerous for journalists to freely roam. The military also does not explain how it differentiates civilian from militant killings, and it has not released a civilian death toll.

The operation has involved fighting in Lower Dir and Buner districts that dates back to last month, but the offensive began in full force in Swat -- the main Taliban stronghold in the northwest beyond the lawless tribal regions -- in early May.

The operation has prompted an exodus of nearly a million civilians, about 100,000 of whom are now staying in relief camps. The military has warned that some militants are trying to flee as well, some after shaving off their beards to blend in with the refugees.

Army spokesman Maj. Gen. Athar Abbas said Saturday that 47 militants had been killed in the previous 24 hours and that one pocket of the valley near the town of Khwazakhela was safe enough for residents to return.

The army has been preparing to assail the Swat Valley's main town, Mingora, where many of the estimated 4,000 Taliban fighters in the valley are believed to be holed up.