At least 10 masked assailants fired from a moving pickup at a police patrol late on Wednesday near Bannu, a town close to the volatile North Waziristan tribal region, said police officer Asif Mahmood on Thursday.
Three police officers were killed and one survived the attack, Mahmood said.
The shooting came on the same day that a roadside bomb explosion killed three soldiers and wounded three others in North Waziristan.
Arab, Central Asian and Afghan fighters with al-Qaeda links, along with pro-Taliban local tribesmen, are believed to be responsible for steady attacks against security forces in North Waziristan and nearby areas such as Bannu.
Also on Thursday, an official revealed that police had arrested a Pakistani TV journalist in March for leaking official secrets after he tried to film an air base once used by US-led forces.
But the reporter's employer protested against his detention and said "his whereabouts are not known".
Mukesh Rupeta, from the privately run Geo TV channel, was detained on March 6 for filming an air base in Jacobabad, southern Sindh province.
US-led forces used Jacobabad as a logistics support base for operations into Afghanistan after the 2001 invasion that toppled the Taliban.
Manzoor Khoso, a senior police investigator in Jacobabad, said that Rupeta and a private cameraman had been arrested and charged for leaking official secrets and would face seven years in jail if convicted.
Rupeta and the cameraman were filming a prohibited area on the base from a nearby building, Khoso said.
Geo issued a statement on Wednesday saying that Rupeta was being held without charge and that an investigation had not been started.
The journalist has been separately charged with making forged passports for members of the minority Hindu community to which he belongs, Manzoor said.