The explosive device planted in a government office in the restive district went off at 11:00 a.m. local time, killing one police and wounding four others, all government's civilian employees, the official said.
Without providing more details, the official said that investigation had been initiated into the incident.
Khawja Ghar district has been regarded as Taliban hotbed in Takhar province with Taluqan as its capital 245 km north of Kabul.
Similarly, an armed militant opened fire on police in the southern Kandahar city on Monday, killing one police and wounding two others, Kandahar's police spokesman Jamal Barikzai said.
However, Barikzai asserted that the attacker had been killed.