Two children and a teenager were critically injured in a powerful blast in Margi Devar village of frontier Kupwara district early on Thursday morning.
The explosion occurred while they were fiddling with an explosive device they had found in the village.
"The condition of the three injured is critical. They have been taken to Srinagar for specialised treatment," a senior police officer said.
The injured were identified as Adil, 18, Mashooq, 14 and Nazia, 11, who are members of the same family. The police officer said the group had found the explosive device in the village and brought it home.
In February, three children of a family were killed in similar circumstances in Maloora village on the outskirts of Srinagar.