Repolling is on in 15 booths in West Bengal and six in Bihar on Sunday amid tight security.
The repolling began at 7 am and is reported to be peaceful.
The 15 polling booths in West Bengal comprise two in Jangipur seat, where External Affairs Minister Pranab Mukherjee is in the fray, besides nine booths in Howrah and Uluberia seats, one in Hooghly seat and three in Burdwan East and Asansol constituencies.
The Election Commission had ordered the repoll due to violence, technical fault in EVMs and other reasons when polling was held in the second phase in the state on May 7.
On that day, in four booths EVMs were smashed by miscreants, while in one booth polling process stopped for over two hours because of violence, state Chief Electoral Officer Debashsis Sen said.
In Bihar, repolling is being held at five booths of Patliputra Lok Sabha seat, where RJD chief and Union Minister Lalu Prasad is one of the contestants and in one booth of Nalanda.
The Election Commission has ordered the repoll as voting there in the fourth and last phase on May 7 was disturbed or delayed for various reasons including malfunctioning of EVMs.
At one of the two booths at naxalite-hit Masaurhi under Patliputra constituency where repolling is on, voting will take place from 7 am to 3 pm. Elsewhere, it will conclude at 5 pm, election office sources said.