People started casting ballot amid a thick security blanket with some 2,500 personnel, including four companies of central paramilitary force, civil police and home guards, deployed in the constituency.
Of the 195 polling stations, 132 have been declared as 'critical'. As many as 76 booths are in Bellary city.
Sreeramulu, a former Health Minister, quit the seat after being indicted in the Lokayukta report on illegal mining and parted ways with the BJP by contesting as an independent.
Gadilingappa is the BJP candidate, while Congress has fielded B Ramprasad in this triangular contest. JDS of former Prime Minister H D Deve Gowda has extended support to Sreeramulu.
The run-up to the election saw fierce campaigning by the three parties, and it has turned out to be a truly prestigious battle, particulary for the BJP.
Polling which began at 8 AM would end by 5 PM. Counting is on December four.
Some 1.72 lakh voters are eligible to exercise their franchise.
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