55 per cent voter turnout has been recorded till 3 pm.
Polling started at 7 AM at Vidisha, Dewas, Ujjain, Mandsaur, Dhar, Ratlam, Indore, Khargone, Khandwa and Betul seats, and will conclude at 6 PM.
A total of 16,95,03,358 voters including 8,78,01,495 men, 8,17,01,514 women and 349 "others" are eligible to exercise their right to franchise, election officials said.
19,446 polling booths are set up for conducting polls in a free and fair manner, they said, adding that among 118 candidates 17 are women.
Prominent among those in the poll arena are Swaraj who is taking on Laxman Singh, former MP and brother of AICC general secretary Digvijay Singh, in Vidisha seat.
Former union ministers Sumitra Mahajan and Kantilal Bhuria are in the fray from Indroe and Ratlam seats respectively.
State unit Congress president Arun Yadav is locked in a straight fight with AAP's Alok Agrawal from Khandwa seat while Premchand Guddu is Congres candidate from Ujjain seat.
Natarajan is seeking a fresh term from Mandsaur seat.
Out of the total 29 seats, polling for nine seats was held in the first phase on April 10 and for ten seats on April 17.
Elaborate security arrangements have been made for conducting polls in a peaceful manner by deploying central and state police personnel.