The poll began at 7 a.m. on Tuesday morning in 23 polling stations and it would continue till 4 p.m. without any break.
In all 15,256 voters, including 7,468 women, are eligible to exercise their franchise to decide the fate of two candidates — Wangpang Konyak of ruling Nationalist Democratic Progressive Party (NDPP) and Congress candidate Wanglem Konyak.
Election officials said that all 23 polling stations are under CCTV surveillance, with seven polling stations identified as vulnerable and six as critical.
The bypoll was necessitated following the death of NDPP MLA Noke Wangnao on August 28.
The counting of votes will be taken up on December 3.
IANS