The incident took place when the children were fiddling with an explosive they had found in the fields at Kumar Mohalla in Hatmulla area of Kupwara, 100 kms from here, police said.
The injured have been identified as 15-year-old Seema Bano, Azad Ahmad Kumar (9) and Faizan Ahmad Kumar (7), the police said.
The injured children have been admitted to a local hospital where their condition is stated to be stable.