The gang entered the house of Pramod, attached to the traffic unit of police, at Mananathavadi late last night and asked him to quit the job, police sources said.
Taking a serious note of the incident, Kerala Home Minister Ramesh Chennithala sought a report about it from the District Superintendent of Police, they said.
The ultras also pasted handbills on the wall of Pramod's house in support of their cause and also set afire his motorbike parked outside.
The state government had in January told the assembly it would step up patrolling and combing operations in forest areas in Kannur, Wayanad, Kozhikode and Malappuram districts in north Kerala following intelligence reports about the presence of Maoists.