Voting began at 7 AM on Saturday for by-polls to the four assembly constituencies of Dinhata in Cooch Behar, Shantipur in Nadia, Khardah in North 24 Parganas and Gosaba in South 24 Parganas districts, an election commission of India (ECI) official said.

In Dinhata, TMC's heavyweight north Bengal leader Udayan Guha is fighting to reclaim the seat which BJP had snatched from him by a whisker in polls held last April.

The by-election at Dinhata was necessitated by the resignation of Nisith Pramanik, now Union Minister of State for Home Affairs, who favoured keeping his Lok Sabha membership over sitting in the opposition in West Bengal's assembly.

Guha, a two-time MLA from Dinhata, is up against BJP's Ashok Mandal, who as a TMC candidate had defeated him, a Forward Bloc candidate then, in 2006.

The bypoll to Shantipur was necessitated by the resignation of BJP MP Jagannath Sarkar, who too resigned from the assembly seat in favour of retaining his Lok Sabha membership.

State minister Sovandeb Chattopadhyay, who resigned from Bhabanipur to facilitate Chief Minister Mamata Banerjee's election to the Assembly, is fighting from Khardah, where TMC's Kajal Sinha died due to COVID-19, just days after polls to the seat were held Bypoll to the Gosaba seat in Sunderbans was also necessitated by the death of TMC's Jayanta Naskar, who too was suffering from Covid.

The EC has deployed 27 companies of central armed forces in Dinhata, 22 in Santipur, 20 in Khardah and 23 in Gosaba, an official said.