Violence broke out when the returning officer declared Tariqul Islam Khan, 45, winner around 8pm on Saturday, said Inspector Md Golam Mostafa of Sadar Police Station.
Tariqul of Notun Bhangabari neighbourhood defeated Shahadat Hossain, a local leader of the ruling Awami League, in the vote.
Their supporters clashed after the results were announced and Tariqul was fatally stabbed. He was declared dead when taken to the hospital.
Inspector Mostafa said the supporters of the two candidates clashed sporadically in Notun Bhangabari and Baparipara neighbourhoods after the news of Tariqul’s death got out.
Additional policemen have been deployed in the areas to control the situation, Mostafa added.
Shahadat could not be reached for comments.