Two died and eight were wounded when a bomb hit a bus carrying police on their way to work near the town of Shirqat, its police chief colonel Majeed Ghatran said.
Another bomb struck a second group of officers that was heading to the location of the first explosion, killing two and wounding three, he said.
No organisation claimed responsibility for the bombings.
Islamic State militants have carried out guerrilla-style attacks in the area since their military defeat in Iraq in December 2017.