Pakistani police say suspected militants killed four officers after opening fire on a police vehicle in the northwestern town of Dera Ismail Khan.
Local police official Mohammad Javed says another two police officers were wounded in Tuesday's attack.
No group immediately claimed responsibility, but suspicion fell on Pakistani militants who have claimed previous attacks across the country.
Dera Ismail Khan is in the Khyber Pakhtunkhwa province bordering Afghanistan. The Pakistani Taliban and other militant groups have long operated it the porous border region.
The latest attack comes two weeks after gunmen stormed a police station, killing eight police officers and a civilian in the southwestern province of Baluchistan. Four militants were also killed in the attack.