Shawkat was arrested on Saturday afternoon from a Rohingya camp in Kutupalong, said Ukhiya police station officer-in-charge Sanjur Morshed.
Armed Police Battalion (APBn) personnel arrested Ziaur and Salam early Friday from Kutupalong camps and Selim from Kutupalong camp-6 at noon that day.
SP Naimul Haque, commander of the 14th APBn, said the three arrestees were later handed over to Ukhiya police station.
Since Mohib Ullah’s murder, patrol by police and APBn personnel been beefed up at the Rohingya camps, the SP added.
On Thursday night, police registered a murder case over Mohib Ullah’s murder following a complaint from Mohib Ullah’s brother Habib Ullah, said officer-in-charge Sanjur Morshed.
Unknown assailants gunned down Mohib Ullah on Wednesday night. He was first taken to a local medical facility and later shifted to Cox’s Bazar Sadar Hospital, where physicians declared him dead.
He was buried in Lambashia camp-1 in Ukhiya upazila on Thursday afternoon after his namaz-e-janaza, which was attended by a large number of Rohingya refugees from camps in Ukhiya and Teknaf upazilas.
Formerly a teacher in Myanmar, the slain activist was popularly known as Master Mohib Ullah among the Rohingya refugees. He was the head of Arakan Rohingya Society for Peace and Human Rights (ARSPH) at Kutupalong camp.