Election Commission sources said that TMC candidate Minati Mishra won the Bankura seat by a margin of 15,139 votes defeating her nearest CPI(M) rival Nialjan Dasgupta.
She bagged 72,954 votes while Dasgupta polled 57,815 votes. BJP candidate Manisha Dey Chatterjee secured 7,910 votes.
Kashinath Mishra whose death caused the by-election in Bankura, had won the seat by a margin of 29,080 votes in 2011 Assembly poll.
TMC candidate Mamata Bhuniya was leading by 15,955 votes in Daspur at the end of the 18th round of counting against Samar Mukherjee of CPIM.
The by-election in Daspur was necessitated by the death of Ajit Bhuniya of TMC.
Ajit Bhuniya had won the Daspur seat by a margin of about 25,000 votes in the last year's Assembly poll.
The Congress, however, did not put up candidate in any of the two seats.