The attack, which triggered a firefight with security forces, happened in the city of Kunduz and also injured nine civilians and a policeman, said provincial spokesman Mahboobullah Shahedi.
One suicide bomber on Tuesday morning detonated a car bomb at the entrance to the office, allowing the other two to get inside, Shahedi said.
"Three guards were killed, nine civilians were injured and one policeman was injured in the blast and fighting," he said.
The local deputy police chief, Abdul Rahman Aqtash, said the fighting had finished after the two remaining bombers detonated themselves inside the offices in quick succession.
He confirmed the death toll given by Shahedi and explained that the nine wounded civilians were residents of a nearby house who were hurt by the initial car bomb blast.
The north of Afghanistan has traditionally been seen as more secure than south and east of the country, which have suffered much of the worst violence in the near decade-long Taliban-led insurgency.
But a string of violent episodes in recent months, including May`s killing of northern Afghanistan`s influential police commander in the province of Takhar, which borders Kunduz, have raised fears about the area`s stability.
(Uu.H-AK/M016)
Editor: Priyambodo RH
Copyright © ANTARA 2011
