The blast on Monday devastated the surrounding area, and investigations are under way to determine the cause.
Police said the arms cache explosion in Baj Ghah village in Baghlan, 125km north of Kabul, burned down four houses.
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".
Afghanistan is awash with old weapons, many of them stored during the resistance against occupying Soviet forces during the 1980s.
Aljazeera's correspondent in Kabul also reported that three women working for a non-governmental organisation in Baghlan were killed on Sunday night.
A group, calling itself the Afghan Youth Renaissance Committee, claimed responsibility for the attack after accusing them of spreading vice.
Elsewhere, two people were killed and four others injured on Monday morning in an explosion in Kandahar province, according to Aljazeera.
Agencies said another blast close to a nearby US military base caused no casualties.
Afghan women working for NGOs
are vulnerable to violent attacks
The first explosion hit a police vehicle near Shah Wali Kot, about 20km north of Kandahar, mayor Ayatullah Khan said. The injured were rushed to a Kandahar hospital with serious injuries, he said.
Khan accused Taliban fighters of planting the bomb, which was made with a land mine, but provided no evidence to back up his assertion.
Later on Monday morning, a blast hit a police pickup truck a few hundred metres from a US base in Kandahar, but caused no casualties, the driver of the vehicle said at the scene. He declined to give his name.
An Afghan soldier helping US troops seal off the site also said no one was hurt.
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.