Chief Minister Mulayam Singh Yadav was leading in Gunnaur but trailing in Bharthana constituency in his home district of Etawah.
Senior Samajwadi Party leader and Minister for Parliamentary Affairs Mohammad Azam Khan, UP Vidhan Sabha Deputy Speaker and BJP leader Rajesh Agarwal and former state BSP President Indrajit Saroj were among those leading in their respective constituencies.
While Khan was leading in Rampur, Agarwal took an early lead in Bareilly city, reports said. Saroj was ahead at Manjahanpur seat.
Independent candidate Akhilesh Singh was leading in Rae Bareli town Assembly constituency.
BJP candidate Satish Mahana was leading against his nearest rival of Congress Ganesh Dixit in the first round of counting from Cantonment Assembly constituency of Kanpur city.
Satish Mahana of BJP was leading by 2,697 votes against his nearest rival Ganesh Dixit of Congress after the first round of counting in Cantonment Assembly constituency of Kanpur city, official sources said.
BSP candidate Anant Mishra was leading by 87 votes against his nearest rival Aruna Tomar of SP after first round counting from Sarsaul Assembly constituency.
While Mishra polled 1,534 votes, Tomar polled 1,447 votes in first round.
BSP candidate Pratibha Shukla was leading by 844 votes against her nearest rival Amitabh Bajpai of SP from Chaubepur Assembly constituency of Kanpur city.
Pratibha polled 1,733 votes and Amitabh Bajpai polled 889 votes after first round of counting.
BSP candidate Anil Shukla Warsi was leading by 1,100 votes against his nearest rival candidate Lal Singh Tomar of Samajwadi Party from Bilhaur Lok Sabha constituency after the first round of counting.
The by-election for Bilhaur Lok Sabha seat took place along with UP Assembly elections. Anil Shukla Warsi polled 1,851 votes, Lal Singh Tomar polled 751 votes.
Congress candidate Sanjeev Dariyabadi was leading by 383 votes against his nearest rival Rakesh Sonkar of BJP from Sisamau Assembly constituency of Kanpur city after the first round of counting.
Dariyabadi polled 1,871 votes as agaisnt Sonkar's 1,488.
In Allahabad, state minister and Samajwadi Party candidate Ujjwal Naman Singh from Karchchna was leading by 1,000 votes over his nearest rival BSP's Collector Pandey.
Puja Pal of BSP is leading in Allahabad West by nearly 2,000 votes over her SP rival Khalid Azim Liyaz Ashraf.
State BJP president Kesari Nath Tripathi was trailing by over 1,000 votes behind Nand Kumar Gupta of BSP from Allahabad south.