Malappuram district is the citadel of the Indian Union Muslim League (Representational)
About 12 per cent polling was recorded in the first two hours of the Malappuram Lok Sabha constituency by-poll that began at 7 am on Wednesday.
No disruptions have been reported from any place as 3,000 security personnel including paramilitary forces oversee the smooth conduct of the by-election.
The election was called after the death of Indian Union Muslim League (IUML) leader E Ahamed.
The IUML has fielded former Kerala Industries Minister PK Kunhalikutty, a sitting legislator and one of the most popular faces of the party.
The Communist Party of India-Marxist has fielded local body member and youth leader MB Faizal and the Bharatiya Janata Party has brought in Sree Prakash.
Soon after casting his vote, Mr Kunhalikutty said the party's victory margin was set to go up.
Mr Faizal said the response from the electorate was positive and they expected secularism to turn out to be victorious.
Mr Prakash said the BJP had constructed roads in the constituency and broken several barriers that prevailed in Malappuram.
Malappuram district is the citadel of the IUML and Mr Ahamed won the 2014 polls with a record margin of 1.94 lakh votes.
But during the 2016 assembly elections the margin of the IUML legislators, who won in the seven assembly constituencies that make up this Lok Sabha seat, came down to 1.18 lakh votes.