Omer Zawak, the spokesman for the provincial governor, says the explosion occurred today at the market in the village of Safar.
Safar is located 70 kilometers (42 miles) from the district centre of Garamser in the volatile province, where insurgents routinely stage deadly attacks.
A police spokesman, Shah Mahmood Hashna, says four children were among the wounded and two of them are in critical condition.
Zawak says he fears the toll could rise because today is the day residents of the area hold their weekly bazaar.