Six of the students with critical splinter injuries were shifted to Srinagar for specialized treatment from Narbal village near Kakapora town.

The tuition-cum-coaching centre was being run in a private school. All educational institutions are closed in the Kashmir Valley these days due to winter recess.

"Eleven of the students are being treated at the Pulwama District Hospital," a police officer said. "The exact facts as to what caused the explosion are being ascertained."

An earlier report said the explosion took place when one of the students was fiddling with a grenade he was carrying.

Meanwhile, clashes broke out between security forces and civilian protesters as news about the explosion spread in Narbal village.