The incident occurred at the Jasimia Model High School in Fulbari Upazila on Wednesday.

Fulbari Police Station OC Bazlur Rashid said the explosion was powerful.

The school’s headmaster Abed Ali said the anti-liberation force had exploded the bomb.

The injured were identified as Nisha, Ayesha, Johura Begum Joba, Labanya and Reshma. All are nine graders of the school.

They were admitted to the Fulbari Hospital.

The hospital’s medical officer Akhtara Begum said the injured students were given saline and other medical aids.

They would recover soon, she said.

Teacher Mahbubul Haque, who witnessed the incident, said the bomb exploded around 1.30pm during a display of human flag arranged by the students.

The participants ran helter-skelter out of panic.

The event was organised by the Fulbari Upazila administration.

Upazila Nirbahi Officer Sheikh Belayet Hossain said it was a stray incident.