Metropolitan Magistrate Shahedul Karim gave the order on Wednesday. the CID had asked for 15 days remand for them.
The five – British-Bangladeshi Touhidur Rahman, Sadek Ali Mithu, Aminul Mallik, Ariful Islam and Jakirul Prakash – are also accused of the murder of writer-blogger Avijit Roy at Dhaka University on Feb 26.
The Rapid Action Battalion (RAB) claims these five had formed a hit squad that was responsible for both the killings.
Rahman is said to be a mastermind and the financier of the group. Rahman, Mallik and Mithu were arrested in Dhaka on Aug 17 for their alleged involvement with banned militant outfit Ansarullah Bangla Team.
Later, they were implicated in the case over Roy’s murder.
On May 12, blogger Das was hacked to death in broad daylight in the same manner in Sylhet as Roy’s killing in Dhaka .
Police earlier arrested photojournalist Idris Ali, former student of Shahjalal University of Science and Technology Mannan Rahi, his brother Mohaiman Noman, and Abul Khayer over Das’ murder.