The BJP is leading in Lucknow Cantt, Ghosi and Balha seats while Samajwadi Party is ahead in Rampur and Zaidpur seats.
The BSP is leading in Iglas and the Apna Dal in Pratapgarh.
The Bharatiya Janata Party (BJP) was all set for celebrations as it was confident of winning maximum seats in the by-elections to the 11 Assembly constituencies, counting for which was underway on Thursday.
"We are going to win all 11 seats," said Deputy Chief Minister Keshav Maurya.
The BJP is contesting 10 seats, having left one (Pratapgarh) for its ally Apna Dal.
The party has an edge in the by-elections that have witnessed a four-cornered contest.
For the Samajwadi Party and the Bahujan Samaj Party, the results were a matter of prestige. Both the parties held one seat each and retaining their constituencies was a major challenge for them.
The Congress has nothing to lose in the by-elections since it did not have even a single seat where by-elections were held.
The by-elections were held in Gangoh, Rampur, Iglas (SC), Lucknow Cantonment, Govind Nagar, Manikpur, Pratapgarh, Zaidpur (SC), Jalalpur, Balha (SC), and Ghosi.
All eyes will be on the Rampur Assembly seat which is seeing a straight fight between BJP's Bharat Bhushan and Samajwadi Party MP Azam Khan's wife Tanzim Fatima. Azam Khan has been slapped with several criminal and land grabbing cases.
According to the state's Chief Electoral Officer, as many as 109 candidates are in the fray.
The maximum number of candidates (13) are from Lucknow Cantonment and the Jalalpur Assembly constituencies, followed by 11 each in Ghosi, Gangoh, Pratapgarh, and Balha. Nine candidates each are in the fray in Govind Nagar and Manikpur, while seven candidates are contesting from Rampur, Iglas and Zaidpur.
( With inputs from IANS )