With this, five suspects have been arrested since the murder on 29 September.
Earlier on Friday two Rohingya men Mohammad Selim,33, and Shawkat Ullah,23, were arrested and on Saturday another two Rohingya men Abdus Salam,32, and Jiaur Rahman,32, were taken into custody. All were arrested from Kutupalong Rohingya camps.
A Cox’s Bazar court on Sunday placed Mohammad Selim and Shawkat Ullah on a three-day remand for interrogation about the killing.
On Thursday night, police registered a murder case following a complaint from Mohib Ullah’s brother Habib Ullah, said officer-in-charge Sanjur Morshed.
Unknown assailants gunned down Mohib on Wednesday night.
Formerly a teacher in Myanmar, the slain activist was popularly known as ‘Teacher’ Mohib Ullah among the Rohingya refugees. He was the head of Arakan Rohingya Society for Peace and Human Rights (ARSPH) at Kutupalong camp.