There was brisk polling Monday in West Bengal's 17 parliamentary constituencies as opposition political parties claimed their polling agents were driven out of booths.
"Till 9 a.m., about 21% of polling has been recorded," an Election Commission official said.
Monday marks the fifth and final phase of polls in the state.
By-elections are also on in two assembly constituencies, Santipur and Chakdaha, in Nadia district.
Opposition political parties claimed that their polling agents were driven out of booths and voters were being prevented from voting or were being intimidated.
A Communist Party of India (CPI-M) agent, who was hospitalised with injuries, said he was assaulted by a group of Trinamool Congress (TMC) activists and was driven out of a polling booth in Dum Dum in North 24 Parganas district.
Congress candidate from Kolkata South Mala Roy alleged that polling agents of her parties were being driven out and the presiding officers trying to obstruct voting.
CPI-M's Dum Dum candidate, Asim Dasgupta, also alleged that Trinamool patronised goons attacked Marxist activists and supporters.
Earlier Sunday, the opposition CPI-M, Congress and the Bharatiya Janata Party (BJP) had urged the Election Commission (EC) to take steps to ensure free and fair polls.
More than 2.56 crore electorate is eligible to vote in 37,670 polling stations for the 17 seats spread across seven districts - Murshidabad, West Midnapore, Nadia, North 24 Parganas, South 24 Parganas, Kolkata and East Midnapore.
A total of 188 candidates are in the fray, including multi-millionaires, cultural figures and political heavyweights.
Firebrand trade unionist Subhashini Ali of the CPI-M takes on Trinamool heavyweight and former railway minister Dinesh Trivedi in Barrackpore.
CPI-M's pharmacologist Sujon Chakraborty is pitted against Netaji's grand nephew Sugato Bose (Trinamool) and painter Samir Aich (Congress) in Jadavpur in what seems like a cliff-hanger.
Among other notable aspirants of the Trinamool are Bengali matinee idol known only as Dev (Ghatal), Mamata Banerjee's perceived political heir and nephew Abhishek Mukherjee (Diamond Harbour) and former union minister Sudip Bandopadhyay (Kolkata North).
The Congress has fielded state president and outgoing MP Adhir Chowdhury (Baharampur) and seasoned campaigner Somen Mitra in Kolkata North. The BJP has nominated state chief Rahul Sinha from the same constituency.
Famed magician P.C. Sorcar Junior is fighting on BJP ticket from Barasat.