The Pakistani army has launched a ground offensive against Taliban militants in North Waziristan.
A statement said operations had begun around Miranshah, the main town in the tribal region bordering Afghanistan.
The offensive follows several weeks of air strikes in which the army says more than 370 militants have been killed.
North Waziristan has long been a sanctuary for militants. Correspondents say many are thought to have left the area before the offensive began.
The assault marks a new phase in operations against the Pakistani Taliban (TTP) and other militants in the area.
Troops were conducting a door-to-door search in Miranshah, the army statement said.
The town has been one of the main TTP bases during recent years when the militants have killed thousands of people in a bombing campaign across Pakistan.
