At least 12,065,803 voters had turned out to vote, equating to 56.17 per cent as of 4 pm.
IEBC said the number is exclusive of those identified by the manual register.
The commission said the by-elections will be held on August 23 in Mombasa and Kakamega where there were ballot mix-ups.
Kitui Rural, Kacheliba, Pokot South, Rongai and Eldas constituents to vote on Wednesday from 6 am.
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