A farmer was hacked to death at Nizputia village in Sadar upazial yesterday.    The victim was identified as Mohidul Islam, 30, son of Abdus Salam of the village. Officer-in-charge of Sadar Police Station Harendranath Sarkar said a gang of criminals numbering five to eight attacked Mohidul with sharp weapons, leaving him dead on the spot. Police recovered the body and sent it to hospital morgue for autopsy. A case was filed with Sadar Police Station in this connection.