"The election to the four Assembly constituencies is going on peacefully. The poll percentage was 24 per cent till 12 noon," an electoral officer told .
The Jalalabad seat saw the highest poll percentage of 29 per cent.
Electors in the four constituencies could be seen reaching polling stations even before voting started at 7 a.m.
The main contest is between the Congress and the Akali Dal-BJP alliance.
Besides, the AAP, the BSP and the Lok Insaaf Party have also fielded their candidates.
Nearly 7.68 lakh voters in all four assembly segments will decide the fate of 33 candidates.
The by-election to the Jalalabad seat was necessitated because of former Deputy Chief Minister and Akali Dal President Sukhbir Singh Badal quitting the seat.
The Dakha seat was vacated by the AAP's H.S. Phoolka and Phagwara by the BJP's Som Parkash.
Mukerian is going to the polls as sitting MLA Rajnish Babbi of the Congress died.
The Congress has fielded former state youth chief Raminder Awla from Jalalabad, Balwinder Singh Dhaliwal from Phagwara, Indu Bala from Mukerian and Sandeep Singh Sandhu from Dakha.
The BJP alliance partner SAD has fielded Manpreet Singh Ayali from Dakha and Raj Singh Dibbipura from Jalalabad.
The BJP has fielded Rajesh Bagga from Phagwara and Jangi Lal Mahajan from Mukerian.
The votes will be counted on October 24.
The Congress has 78 legislators in the 117-member House.
( With inputs from IANS )