Here are the top 10 points on the bypolls:
The Assembly seats going to polls comprise Rampur Sadar and Khatauli in Uttar Pradesh, Kurhani in Bihar, Bhanupratappur in Chhattisgarh, Sardarshahar in Rajasthan and Padampur in Odisha.
For the big Mainpuri fight, the Akhilesh Yadav-led party has fielded his wife and former MP Dimple Yadav. The party's campaign saw Mr Yadav's show of unity with his estranged uncle Shivpal Yadav.
About 3 hours after voting began, Dimple Yadav tweeted that she had been trying to reach the district magistrate to flag polling irregularities, but her calls were not answered.
The Samajwadi Party chief then addressed the media, acusing the police and the local administration of preventing people from casting their votes at polling booths in Mainpuri and Rampur. "There are videos that show that police are stopping people from voting in Rampur. What are the Election Commission's guidelines?"
Targeting the Yogi Adityanath-led state government, he said, "I don't know on whose orders the administration is working. What briefing has been given to them? Complaints are coming continuously since morning. Police are not allowing people to cast votes."
State BJP president Bhupinder Singh Chaudhary trashed the allegations and said the Akhilesh Yadav-led party is headed for a defeat in all the three seats polling today.
In Mainpuri, the BJP has fielded former MP Raghuraj Singh Shakya. Mulayam Singh Yadav held this seat for five terms, but his victory margin last time was slim. This has sparked speculation that his daughter-in-law may not have a smooth sail this time.
In Rampur Sadar and Khatauli, elections are being held after Samajwadi Party MLA Azam Khan and BJP MLA Vikram Singh Saini were disqualified after conviction in criminal cases. While Azam Khan got a three-year jail term in a hate speech case from 2019, Vikram Saini was convicted in a riots case.
In Rampur Sadar, the BJP has fielded Akash Saxena, son of former party MLA Shiv Bahadur Saxena, against Azam Khan's protege Asim Raja. In Khatauli, Vikram Singh Saini's wife Rajkumari Saini is contesting against RLD's Madan Bhaiya.
By-elections in Rajasthan, Chhattisgarh and Odisha are being held due to the deaths of the sitting candidates. In Bihar, the sitting MLA of Tejashwi Yadav's Rashtriya Janata Dal was disqualified. This would be the first contest between Chief Minister Nitish Kumar's Janata Dal United and estranged ally BJP.
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