The districts where polling were held included Bijnor, Saharanpur, Moradabad, Sambhal, Rampur, Bareilly, Amroha, Pilibhit, Kheri, Shahjahanpur and Badaun.
A total of 2.28 crore voters, including over 1.04 crore women, are eligible to cast their ballots in 14,771 polling centres and 23,693 polling stations in the second of the seven-phase polling.
"Polling was held peacefully amid tight security," UP Chief Electoral Officer T Venkatesh said.
The CEO office said the average turnout was over 65 per cent in these seats.
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115-year-old grandfather Z H Kazmi cast his ballot assisted by his family members.
At certain places, long queues were seen outside polling stations. First time voters were seen enthusiastic, taking selfies and proudly showing off the indelible ink imprint on their fingers.
Muslim women clad in burqas were seen outside several booths, while the photograph of a newly married couple going to cast vote in Bareilly went viral on social media.
Of the 67 seats at stake, the ruling Samajwadi Party had won 34 seats in the 2012 polls, followed by BSP 18, BJP 10, Congress three and others two.
The prominent contestants include controversial SP minister Azam Khan and his son Abdullah Azam, who are contesting from Rampur and Swar seats respectively, Saif Ali Naqvi, son of former Congress MP Zafar Ali Naqvi, former central minister Jitin Prasada from Tilhar (Shahjahanpur), BJP Legislature Party leader Suresh Kumar Khanna from Shahjahanpur city and state minister Mehboob Ali from Amroha.
Elaborate arrangements were made for free and fair polling with deployment of 51,771 police constables, 52,598 homeguards, 5,397 sub-inspectors and 3,666 head constables to maintain law and order.
The Commission said the decision was taken in view of past instances of advertisements of "offending and misleading nature" in print media on such occasions, which vitiate the elections.
The upcoming five phases of polling will be held on February 19, 23, 27 and on March 4 and 8. Counting of votes will be taken up on March 11.