The deceased was identified as Jahirul Hoque Jahir, 48, imam at Krishnarampur Jame mosque.
Police sent the body to Noakhali Medical College Hospital morgue for an autopsy.
Sudharam model police station OC Anwar Hossain, quoting Jahir's wife Abu Hafsa, said Jahir had been suffering from mental disorder and started living alone in a room 15 days ago.
He had his dinner around 11pm on Thursday night and went to sleep in his room. After some time, the couple's younger son found the throat-slit body of his father laying on bed and a knife in his right hand, the OC said.
“According to Hafsa's statement, we initially suspect that it is a suicide incident. However, the fact can be known only after the post-mortem report,” the OC continued.