Polling was underway on Monday for the bypolls to four assembly seats: Phagwara (reserve), Jalalabad, Dakha and Mukerian in Punjab.
Polling began at 7 am and will continue till 6 pm, officials said.
Around 7.76 lakh voters are eligible to decide the fate of total 33 candidates.
The results of the elections will be declared on October 24.
Till 9 am, polling percentage in Phagwara was 7.6 per cent, 12 per cent in Mukerian, 6.54 per cent in Dakha and 14 per cent in Jalalabad, officials said.
There was no report of any untoward incident in these four assembly segments, they said.
Seven companies of paramilitary forces have been deployed in four assembly segments, a poll official said.
A total 920 polling stations have been set up. Some polling stations in Dakha and Jalalabad have been categorized as sensitive.
In the last elections, while the SAD-BJP combine had bagged two of the four assembly segments, one each was won by the Congress and the Aam Aadmi Party (AAP).
This time, the main contest is between the Congress and the SAD-BJP combine.
The ruling Congress would like to maintain its winning momentum in the bypolls to four assembly seats while the Shiromani Akali Dal-Bharatiya Janata Party alliance and AAP would also hope to revive their political fortunes in these by-polls.
While the Shiromani Akali Dal (SAD) is contesting the Jalalabad and Dakha seats, its ally BJP has fielded candidates in Phagwara and Mukerian.
In Phagwara (reserve), the main contest is between Congress candidate and former IAS officer B S Dhaliwal and BJP's Rajesh Bagha. Besides, the AAP, BSP and the Lok Insaaf Party have also fielded their candidates.
The Phagwara seat fell vacant after sitting MLA Som Parkash was elected to the Lok Sabha from Hoshiarpur.
On the Dakha seat, the Congress has fielded Sandeep Sandhu, political secretary of Chief Minister Amarinder Singh.The SAD nominee from the seat is former MLA Manpreet Singh Ayali.
The Dakha seat fell vacant following the resignation of former AAP leader and noted Supreme Court lawyer H S Phoolka from the state assembly.
In Jalalabad, considered as an Akali bastion, there is a straight contest between SAD's Raj Singh Dibipura and Congress's Raminder Singh Awla.
The Jalalabad seat fell vacant after sitting MLA and SAD chief Sukhbir Singh Badal was elected to the Lok Sabha from Ferozepur parliamentary segment in the 2019 general election.
From Mukerian, the Bharatiya Janata Party has fielded Jangi Lal Mahajan.The Congress nominee is Indu Bala, the wife of the late Congress MLA Rajnish Kumar Babbi, whose death necessitated the by-elections.
In the 117-member Punjab Assembly, the Congress at present has 77 legislators.The SAD has 13 MLAs while the strength of AAP legislators is 19.The BJP and LIP have two MLAs each.