Chennai City Police Commissioner AK Viswanathan said they had ensured to conduct a fair election and have deployed additional forces to maintain peace and harmony.
"We will ensure free and fair elections, today. We have deployed additional forces," Viswanathan said.
Bharatiya Janata Party (BJP) candidate Karu Nagarajan and Dravida Munnetra Kazhagam (DMK) candidate N Marudhu Ganesh have also cast their votes.
Counting of votes will be held on December 24.
The by-polls were earlier scheduled for April 12 earlier this year, but were cancelled following allegations that sums of money were distributed in a vote-for-cash scam.(ANI)