Uttar Pradesh's ruling BJP was leading in the Gorakhpur Lok Sabha constituency while the opposition SP was ahead in Phulpur after three hours of counting for the parliamentary by-elections, Election Commission officials said.

In Gorakhpur, the bastion of Chief Minister Yogi Adityanath, BJP's Upendra Dutt Shukla was leading by 1,666 votes over his nearest SP rival Praveen Nishad.

In Phulpur, SP's Nagendra Pratap Singh Patel was ahead by 3,600 votes with BJP's Kaushalendra Singh Patel trailing behind him.

The results are expected to be declared by afternoon, an EC official said.

Ten nominees were in the fray from Gorakhpur, while 22 candidates contested from Phulpur.

According to the EC, there are 19.61 lakh voters in the Phulpur parliamentary constituency and 19.49 lakh in the Gorakhpur Lok Sabha seat.

The bypolls were necessitated after  Adityanath and his Deputy Chief Minister Keshav Prasad Maurya vacated the Gorakhpur and Phulpur Lok Sabha seats respectively, following their election to the state legislative council.

Gorakhpur is significant for the BJP with Adityanath representing the seat in the Lok Sabha five times. Before him, his mentor Yogi Avaidyanath was MP from the seat.

Phulpur, once represented by the country's first prime minister Jawaharlal Nehru, witnessed a saffron surge in the 2014 Lok Sabha election when Maurya won the seat.