The deceased was identified as Mokarim Mia, 18, son of Faruk Mia of Bhirar Bhita village under Chawganga union in the upazila.
According to police and local sources, Mokarim and his uncle Babul Mia locked into an altercation around 8:30pm at the courtyard of their house over fishing in the haor.
At one point, Babul allegedly stabbed Mokarim with a sharp weapon, leaving him critically injured.
He died on the waywhile family members were taking him to Kishoreganj General Hospital, reports UNB.
Legal steps will be taken upon investigation, said Officer-in-Charge (OC) of Itna Police Station Md Zafar Iqbal.