The spokesman for the provincial police, Jawed Basharat, says the worshipers had finished their evening prayers at a mosque in the provincial capital of Puli Khumri and were waiting for food deliveries when the bomb went off on Monday evening.
The spokesman says the food was donated by the acting provincial governor Sultan Mohammad Ebadi, who was at the prayers.
Food donations and evening iftar meals provided for the poor are typical during the Muslim holy month of Ramadan.
Basharat says one member of the local provincial council was among those wounded in the blast. No group one immediately claimed responsibility for the explosion.