Polling in by-elections to three Lok Sabha seats and one assembly seat in West Bengal began amid tight security on Saturday morning.
The Lok Sabha constituencies are Malda, Purulia and Katwa, while the assembly seat is from Bongaon in North 24 Parganas district.
"The polling has been peaceful so far with no untoward incident. In the first three hours, 20 per cent polling was reported," state chief electoral officer Debasish Sen said.
The by-election to Malda and Katwa (in Burdwan district) was necessitated by the deaths of veteran Congress leader ABA Ghani Khan Chowdhury and Mehboob Jahedi (Communist Party of India-Marxist) respectively.
In Purulia, the election has been necessitated by the conviction in a rape case of All India Forward Bloc MP Bir Singh Mahato.
The assembly seat from Bongaon had earlier been held by Trinamool Congress member Bhupen Seth, who died recently.
About 70 companies of paramilitary forces besides armed police, Rapid Action Force and District Armed Police have been put in position.
Eleven Election Commission observers have also been deployed.