Roads in Darzaab in northern Jawzjan province were blocked by 50 centimetres of snow, cutting off access for villagers in the area to medical care as temperatures plunged to -10 degrees Celsius.
"Unfortunately we have 27 children killed due to heavy snowfall and freezing weather," district governor Rahmatullah Hashar told AFP, saying the deaths had occurred over the last two or three days.
All the children were under the age of five, he said, adding the blocked roads mean the toll could still increase.
Heavy snowfall and avalanches kill scores of people in Afghanistan each winter.
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In 2015, avalanches killed some 300 people across the country, the bulk of them in the mountainous province of Panjshir, north of Kabul.
Rescue efforts after disasters such as avalanches and flash floods, which often hit as snows melt in the spring, are frequently hampered by lack of equipment.
Poor infrastructure makes it difficult for rescue teams to reach isolated areas.