The explosion in the village of Bashgah in Baghlan province, some 120km north of Kabul, reportedly razed the neighborhood.
Police chief General Fazeluddin Ayar said the wounded people were taken to a local hospital for treatment.
It was unclear what set off the explosion of the weapons in the store, which Ayar said dated from "a long time ago".
In other developments, a remote-controlled bomb injured two police officers and injured four in Shah Wali Kot, about 20km north of Kandahar.
According Al Jazeera, violence between Taliban-led fighters and Afghan and US-led forces has intensified in recent weeks, leaving dozens of fighters and at least two coalition soldiers and several civilians dead.