Additional Deputy Commissioner of Sylhet Metropolitan Police (SMP) Jotirmoy Sarkar confirmed the development.
Besides, three policemen have been withdrawn in this connection.
Earlier, Rayhan Ahmed, 34, a resident of Akharia in Sylhet city, was beaten to death in police custody on Sunday, said the family of the victim.
His wife Tahmina Akter Tanni filed a case at Kotwali Police Station early Monday accusing a number of unidentified people.
Police rejected the allegation and said Rayhan was caught by locals of Kastghar area during robbery and was lynched.
Jotirmoy said they are investigating the matter. A probe body has been formed to look into the incident.
Meanwhile, locals demonstrated at Akhalia around 3pm demanding justicefor Rayhan.
“My son is not a mugger. Police caught him and took him to Bandarbazar outpost where he was tortured to death. Police are the protectors of the people but they killed my son for money. Rayhan has a two-month old girl. When she grows up, how should I console her?” she asked.
Several hundred people also formed a human chain.
The protesters also threatened to go for tougher movement if those involved in the killing are not brought to book within 72 hours.
Also read: Case filed over man’s death ‘in Sylhet police custody’