The most keenly-watched contest is in Varanasi, where Bharatiya Janata Party’s prime ministerial candidate Narendra Modi is locked in a battle against Aam Aadmi Party chief Arvind Kejriwal and Ajay Rai of the Congress.
Samajwadi Party chief Mulayam Singh Yadav is contesting from Azamgarh, while Quami Ekta Dal leader Mukhtar Ansari is in the fray from Ghosi.
Congress has fielded Bhojpuri actor Ravi Kishan from Jaunpur.
A total of 328 candidates are in the fray. Over three crore are eligible to vote.
Balloting is taking place at 31,483 polling stations where more than 146,000 personnel have been deployed.