Pakistan's military launched a ground assault in North Waziristan tribal area on Monday, beginning a new phase in its offensive against Taliban militants, officials said.
Troops moved on Miranshah, the main town in North Waziristan, around 9:30am (0430 GMT) after two weeks of air strikes and artillery bombardment of insurgent targets.
Washington has long urged Islamabad to tackle militant sanctuaries in North Waziristan, a haven for Pakistani Taliban and Al-Qaeda-linked insurgents.
Security officials in Miranshah told AFP troops moved on the town after six hours of artillery shelling, which began at 3:30am.
"They are using tanks and armoured vehicles for ground movement," a security official said on condition of anonymity.
"The forces have also taken over the civil hospital in Miranshah and have destroyed four hideouts in the artillery firing."
Other security officials in Peshawar, the main city of northwest Pakistan, confirmed the advance, saying forces had also moved on the town of Mir Ali.
A statement from the military's communications wing said infantry troops were carrying out house-to-house searches.