Dravida Munnetra Kazhagam (DMK) on Saturday took an early lead in the Vikravandi Assembly constituency, where the counting of votes polled in the July 10 bypoll was underway.
According to reports, DMK nominee Anniyur Siva was leading ahead of his nearest PMK rival, C Anbumani, by about 5,000 votes.
Counting of votes began at 8 am with postal ballots being taken up first.
The by-election was necessitated due to the death of DMK legislator N Pugazhenthi in April this year.
The DMK-led alliance had won all 39 Lok Sabha seats in Tamil Nadu and the lone Puducherry segment in the just concluded Parliamentary elections.