Abdullah Hsrat, spokesman for the provincial governor, says two border police officers and two civilians were killed in the attack, which took place in Zazi Aryub district on Sunday night.
He says the explosion also wounded two other policemen. No group immediately claimed responsibility for the bombing but the Taliban have stepped up their attacks against the Afghan security forces across the country.
Separately, Hsart says a dispute between two rival Taliban commanders in the same province set off clashes over the weekend that left at least five insurgents dead.
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