Here are the 10 developments of the story:
Over 1.2 crore people voted for 73 seats spread across 15 districts to decide the fate of 839 candidates.
Security was tight in the western city of Muzaffarnagar, where over 60 people were killed and tens of thousands were displaced in riots in 2013.
Brother of controversial BJP legislator Sangeet Som, accused of making inflammatory speeches ahead of the deadly riots, was detained this morning in Faridpur for carrying a pistol inside a polling booth, a senior police officer said.
The BJP, SP-Congress alliance and the BSP are locked in a close contest in western UP, with Ajit Singh of the Rashtriya Lok Dal or RLD hoping to consolidate some of the Jat vote once again and push back into political relevance.
The BJP has projected no chief ministerial candidate for the UP elections and has built its campaign around PM Modi's appeal. In his campaign, PM Modi has said that in banning 500 and 1,000 rupee notes, a move aimed at eliminating black or undeclared money, he had the interests of the poor at heart. A strong showing in UP, country's most populous state, would strengthen his chances of a second term in 2019.
The BJP polled 42 per cent of the vote in Uttar Pradesh in the 2014 general election, sweeping 71 out of 80 seats. In the region voting on Saturday, it had won Lok Sabha seats equal to over 65 of the 73 assembly segments.
The ruling Samajwadi Party is led by 43-year-old Chief Minister Akhilesh Yadav who rebelled against his father and has teamed up with the Congress in a strong combination. The SP had won a majority in the last state assembly election, in 2012, with just 29 per cent of the vote.
In western UP the Samajwadi Party and Congress hope to consolidate the significant Muslim vote - 17 per cent of the state's total population - with the partnership - they split the vote in previous elections. Ms Mayawati, who hopes to wrest back the state she lost in 2012, too is eyeing the Muslim vote to supplement her Dalit support base that constitutes 21 per cent of the population. She has fielded almost 100 Muslim candidates this time.
Among candidates who were being watched closely on Saturday's elections are first time contestants Mriganka Singh (Kairana) and Pankaj Singh, son of union Home Minister Rajnath Singh, from Noida seat.
In the 2012 assembly elections the BJP had won 11 of the 73 seats that were voting on Saturday. The Bahujan Samaj Party and SP had won 24 seats each, Rashtriya Lok Dal had won nine and Congress five. Apart from the 24 seats it won in 2012, the BSP had finished second on over 30 seats.
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