Ultras of the banned Dima Halam Daogah (Jewel) stormed the jail in Haflong early Thursday, which is near to the Haflong police station, and freed three of their members.
"A group of about seven DHD(J) cadres threw grenades and fired at the jail at around 5.25 am. And then stormed the premises to take away their three dreaded members," police said.
None was, however, injured in the attack.
The three who were freed were identified by the jail authorities as Daniel Dimasa, Daku Dimasa and Malu Dimasa.
North Cachar Hills police superintendent has suspended the policemen who were on duty during the attack.