The attack occurred around noon in Imam Sahib district of Kunduz province, said district police chief Abdul Qayum Ebrahimi. [break]
He said the district police and a government office that distributes official identification papers are both located in the building that was hit by the explosion.
"Today it was very crowded," Ebrahimi said. "People had gathered in the front of the department to get identification cards."
He said an unknown number of people were wounded.
There has been sharp slide in security in recent months in Kunduz and other northern provinces, where there are known hide-outs for the Taliban, al-Qaida and fighters from other militant factions, including the Haqqani network, Hizb-i-Islami and the Islamic Movement of Uzbekistan.
NATO has sent more troops to the north and has been pushing harder into militant-held areas.
Earlier this month, a bomber killed the district chief of Chahar Dara in Kunduz province.
In October last year, a powerful bomb killed the governor of Kunduz, Mohammad Omar, and 19 others in a crowded mosque in neighboring Takhar province.
Omar was killed just days after he publicly warned of escalating threats from Taliban and foreign fighters across the north.
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