The 57 seats, including 13 reserved for SCs and three for STs, are in Uttar Pradesh and Punjab (13 each), West Bengal (9), Bihar (8), Odisha (6), Himachal Pradesh (4), Jharkhand (3), and Chandigarh (1).

Over 10.06 crore voters - 5.24 crore males, 4.82 crore females, and 3,574 belonging to the third gender - are eligible to head to 1.09 lakh polling stations to choose their preferred candidates from the 908 nominees in the fray.

The Election Commission said that around 10.9 lakh polling officials have been deployed and "polling stations are ready to welcome the voters with all basic facilities including ample shade, drinking water, ramps, and toilets to ensure that polling takes place in a comfortable and secure environment".

"Concerned CEOs and state machineries have been directed to take adequate measures to manage the adverse impact of hot weather or rainfall wherever predicted," it added.

Polling will also be held for the remaining 42 seats in Odisha in the simultaneous Assembly elections, while there are six bypolls in Himachal Pradesh whose outcome will determine the fate of the state's Sukhvider Singh Sukhu-led Congress government.

Prime Minister Narendra Modi (Varanasi) heads the list of prominent Lok Sabha candidates in this phase, while the other BJP candidates include Union Minister Anurag Thakur from Himachal Pradesh's Hamirpur, former Union Minister Ravi Shankar Prasad from Patna Sahib, actress Kangana Ranaut from Himachal Pradesh's Mandi, and ex-IFS officer and former envoy to US Taranjit Singh Sandhu from Amritsar.

Congress candidates include former Union Ministers Manish Tewari from Chandigarh and Anand Sharma from Himachal's Kangra, former Himachal CM Virbhadra Singh's son Vikramaditya Singh from Mandi, former Punjab CM Charanjit Singh Channi from Jalandhar, and state unit chief Amarinder Singh Raja Warring from Ludhiana.

The other significant candidates are West Bengal Chief Minister and Trinamool Congress supremo Mamata Banerjee's nephew Abhishek Banerjee from Diamond Harbour, SAD leader and former Union Minister Harsimrat Kaur Badal from Bathinda, Samajwadi Party's Kajal Nishad from Gorakhpur, where the Bhojpuri actress takes on industry star and sitting BJP MP Ravi Kishan, and CPI-M's Saira Shah Halim against sitting Trinamool MP Mala Roy from Kolkata Dakshin.