They had fled across the border to Bangladesh amid heavy fighting between the Myanmar military and rebel insurgents in Rakhine
Chittagong Metropolitan Police on Monday said they sought 15 days to interrogate the five, shown arrested under Section 54 for suspicion.
Pakistani citizen Mohammad Alam, 44, along with four Bangladeshis – Abdul Majid, 31, Md Amin, 50, Md Shafiullah, 38, and Md Salamat Ullah, 40 – were detained from the city's Nasirabad on Sunday.
Alam is director of Netherlands-based voluntary organisation 'Global Rohingya Centre'.
Shafiullah is Awami League's Naikhyanchharhi Upazila unit human resource affairs secretary. He contested this year's Upazila polls with blessings from the party but lost.
Police suspect the five have links with Rohingya extremist outfit RSS.