The by-elections took place in Noapara and Uluberia in West Bengal and Ajmer, Alwar and Mandalgarh in Rajasthan.
Jaipur/Kolkata: The Congress was maintaining a significant lead in Alwar and Ajmer Parliamentary seats in Rajasthan and it moved ahead in Mandalgarh assembly seat where the BJP was leading initially, as per trends available in the counting of votes for the bypolls.
In Alwar, Congress candidate Karan Singh Yadav was leading by 39,826 votes over his nearest rival, Jaswant Yadav from the BJP, after 15 rounds of counting.
Yadav had garnered 1,63,489 votes.
In Ajmer, Congress' Raghu Sharma was maintaining a lead of 23,882 votes over BJP candidate Ram Swaroop Lamba.
In Mandalgarh, where the BJP was maintaining a lead in the beginning, Congress' Vivek Dhakad won by 12976 votes.
Congress dissident Gopal Malviya, who was running as an independent, garnered 22,310 votes.
The BJP had won all the 25 Lok Sabha constituencies in the state in the 2014 general elections.
The party, which wrested power from the Congress in 2013 in Rajasthan, had 161 MLAs in the House of 200. It had strategised raising the tally of seats to 180 in the Assembly polls due this year end.
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In West Bengal, the Trinamool Congress on Thursday surged ahead of its rivals in both Noapara Assembly seat and Uluberia Parliamentary constituency after the initial rounds of counting of votes for the bypolls.
TMC won Noapara Assembly bypoll in West Bengal.
TMC candidate Sunil Singh secured 46,281 votes whereas his nearest rival of CPI(M), Gargi Chatterjee, bagged 16,444 votes.
Sandip Banerjee of the BJP secured 15,570 votes whereas Goutam Bose of the Congress managed to get just 4,742 votes.
The TMC also took an early lead in the Uluberia Lok Sabha byelection by a margin of 4,767 votes.
After the first round of counting in Uluberia Lok Sabha seat, TMC candidate Sajda Ahmed secured 6,462 votes, whereas CPI(M) candidate Sabiruddin Molla bagged 1695 votes.
Anupam Mallik of the BJP and S K Madassar Hossain Warsi of the Congress managed 1,471 and 256 votes respectively.
The elections to both the seats were held on February 29.
The bypolls were necessitated following the deaths of Sultan Ahmed, the sitting TMC MP from Uluberia Lok Sabha constituency in Howrah district, and Madhusudan Ghose, Congress MLA from Noapara assembly seat in North 24 Parganas district.
Sajda Ahmed, the TMC candidate from Uluberia parliamentary seat, is the wife of Sultan Ahmed.