Voting in the by-elections for four Tamil Nadu Assembly constituencies - Aravakuruchi, Sulur, Thiruparankundram and Ottapidaram - began on Sunday morning.
Similarly, repolling in the 13 booths in Erode, Dharmapuri, Tiruvallur and Cuddalore Lok Sabha constituencies in Tamil Nadu started at 7 am.
Voters in these four constituencies will decide the electoral fate of 137 candidates in the fray.
However, the main contest will be between the ruling AIADMK, principal opposition party DMK, and an Independent legislator T.T.V.Dhinakaran-floated AMMK party.
Actor-politician Kamal Haasan's party Makkal Needhi Maiam (MNM) candidates are also in the contention.
By-elections for 18 Assembly constituencies were held on April 18 along with the Lok Sabha polls in the state.
According to Election Commission about 16,000 police personnel will be deployed in the four assembly seats for security purposes.
The results of the by-polls for 22 assembly constituencies are crucial for ruling AIADMK, opposition DMK and AMMK parties.