Police said a clash broke out between the supporters of AL-backed candidate and independent candidate at Nayanpur Primary School in Ichapur union around 5:00pm, leaving Sajib seriously injured after being hit on his head.
Later, he was sent to Chandpur Sadar Hospital where the physician declared him dead on arrival.
Lakshmipur police superintendent AH Kamruzzaman said they are investigating the matter.
Meanwhile, the law forces detained 40 people from different places of the upazila.