"An improvised explosive device (IED) was planted near a boys' school in Pusht Rod district. A student stepped on the device, causing an explosion around midday. As a result, two children were killed and three wounded," provincial government spokesman Abdul Rahman Zhwandoy told Xinhua.
All the victims were boys and the injured have been admitted to a district hospital, he added.
No group has claimed responsibility for the blast.
No group has claimed responsibility for the blast but Afghan Taliban militants often attack Afghan and NATO-led forces with IEDs, which also inflict casualties on civilians.
The UN Assistance Mission for Afghanistan (UNAMA) has said that more than 1,300 civilians were killed and over 2,500 others injured in Afghanistan from January to June this year.
Of the total casualties, 231 children were killed and 529 wounded, IED explosions being the leading cause of the fatalities.