Polling is on by and large peacefully in 51 Assembly constituencies spread over 11 districts of the state.
"Over 25 per cent polling was recorded till noon," poll officials said here.
The voting was slow in the first two hours but picked up pace as the day progressed.
Prominent contestants in this phase include controversial minister Gayatri Prasad Prajapati from the ruling Samajwadi Party, who will be facing Amita Singh from Congress and BJP's Garima Singh in Amethi, the Lok Sabha constituency of Rahul Gandhi.
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Amita, wife of Congress leader Sanjay Singh, hoped people would support the best candidate "and I will definitely win."
Garima, the first wife of Sanjay, on the other hand said there was no development in the constituency and people were facing problems.
The districts going to polls in this phase are Balrampur, Gonda, Faizabad, Ambedkar Nagar, Bahraich, Shravasti, Basti, Siddharth Nagar, Sant Kabir Nagar, Amethi and Sultanpur.
Elaborate arrangements have been made to ensure free and
fair conduct of polls.
Indo-Nepal, inter district and inter-state borders have been sealed, while central para-military forces conducted flag march in sensitive areas to instill confidence among voters.
Due to the death of SP candidate Chandrashekhar Kanaujia in Alapur (Ambedkar Nagar), the EC has announced fresh date of voting in this constituency on March 9.
The ruling SP had won 37 seats out of 52 (total seats in this phase including Alapur) in the 2012 Assembly polls. While BJP and Congress won five seats each, BSP had won 3 and Peace Party 2.
In all, 607 candidates are in the fray in this phase with the maximum of 24 candidates in Amethi and minimum of six each in Kapilvastu and Etwa seats in Siddharth Nagar district.
Over 1.81 crore voters, including over 84 lakh women, will decide the fate of ministers Vinod Kumar Singh alias Pandit Singh from Tarabganj (Gonda), Tej Narain Pandey alias Pawan Pandey from Ayodhya and BSP state president Ram Achal Rajbhar from Akbarpur, among others, in this phase.
12,555 polling centres and 18,822 polling booths are in this phase.
The turnout in these constituencies in 2012 was 57.09 per cent.