SP Naimul Haque, commander of the 14th armed police battalion, said APBN members detained the suspect from camp-6 at Kutupalong in Ukhiya upazila at around 11:00 am.
Later, he was handed over to Ukhikya police station, said the SP.
Earlier on Thursday night, police have registered a murder case in connection with the killing of Rohingya leader Mohib Ullah at Ukhiya camp in Cox's Bazar on Wednesday night.
The FIR for murder was filed against unknown persons at the Ukhiya police station on a complaint from Mohib Ullah's brother Habib Ullah, said officer-in-charge Sanjur Morshed.
Unknown assailants gunned down Mohib on Wednesday night. He was first rushed to a local medical facility and later shifted to Cox's Bazar sadar hospital, where doctors declared him dead on arrival.
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.