The detainees are Nazrul Islam, 45, and Hazrat Ali, 48. They were arrested from BSCIC Bus Terminal of Shahjadpur municipality on Friday night.
Shahjadpur police Inspector Md Monirul Islam, also the investigation officer of the case, said that they had arrested the duo based on findings of the investigation and video footage captured during the shooting.
They would be sent to the court on Saturday, said the OC.
A total of 12 people, including Shahjadpur Mayor Halimul Haque Miru and his two brothers, have been arrested so far in the murder case.
Journalist Shimul was hit by a bullet fired by Miru on February 2, during a clash between the supporters of Chhatra League President of Shahjadpur Government College unit Bijoy Mahmud and the supporters of the mayor’s brother Pintu. Shimul died the following day while being taken to Dhaka.
Shimul’s wife filed a case against 18 people for the murder.


