The bypolls are being held in Porbandar and Banaskantha Parliamentary constituencies and the Assembly seats of Jetpur, Dhoraji, Limbdi and Morva Hadaf.
In view of heat conditions, Election Commission has extended the voting timing. The voting began at 7 am and shall continue till 6 pm (usual timing is 8 am to 5 pm), election officials said.
Eighteen candidates are in the fray for the four Assembly segments and 15 for the two Lok Sabha seats.
Former Congress MP Vitthal Radadia and his son Jayesh, after joining ruling BJP, will be testing political waters from Porbandar (LS seat) and Jetpur (Assembly), respectively.
The counting will take place on June 5.