Locals said 34 died but the figure could not be independently confirmed.
Up to 70 others were injured when the arms cache of an Afghan faction leader exploded in a tiny farming village in Baghlan province some 180km north of Kabul.
The explosion highlighted the continuing difficulties in disarming Afghanistan's private militia forces after some 25 years of warfare and civil strife.
"I heard a heart-shaking, dreadful explosion and saw black smoke around the commander's house and then I fainted," local farmer Ghulam Mohaiudin said, his hand and right eye covered with bandages.
"When I became conscious I heard screams and noises and there were dead and injured people around everywhere."
Women and children
Afghan interior ministry spokesman Lutfullah Mashal said the toll was now 29. "An investigation team has reached the area from Kabul and the provincial police are also investigating," he added.
"I heard a heart-shaking, dreadful explosion and saw black smoke around the commander's house and then I fainted"
Local farmer Ghulam Mohaiudin
Jalal-e-Bachgah, the Afghan faction leader who stockpiled the arms, survived the blast as he was in a nearby village visiting his second wife. But his 16-room house was completely destroyed and most of his neighbours and relatives died.
His mother and sister were injured.
Villagers said they had buried 23 people and were still digging through the debris. One witness who helped pull bodies from the rubble said women and children were among the victims.
Afghanistan remains awash with weapons and powerful faction leaders still rule much of the country, with the central government's power barely extending beyond capital Kabul.
Jalal-e-Bachgah had previously said he had "disarmed and had no more weapons".