Superintendent of Police (SP) AHM Abdur Rokib disclosed this while briefing the newsmen at his office in Chapainawabganj on Monday.
The arrestees are-- Md Mesbaul Hoque Tutul, 42, Md Masud Rana, 38, Md Ibrahim alias Daud Ibrahim alias Haba, 32, Md Shamim Reza, 35, and Md Milon Hossain, 30.
The official said that former Juba League leader and former councilor of Shibganj municipality Khairul Alam Jem was stabbed by the accused in Udayan More area of the town at 6.20 pm on April 19.
The injured was taken to the Chapainawabganj District Hospital where the on-duty doctors declared him dead at 8.30 pm.
Jem's elder brother, Monirul Islam, later filed a murder case with Chapainawabganj Sadar Model Police Station on April 22, he added.
He said police of Chapainawabganj Sadar and the Detective Branch (DB) conducted joint drives and arrested them.