The main contest is between CPI(M)-led Left Front and Trinamool Congress-Congress alliance. BJP has also fielded candidates in 49 seats.
Multi-cornered contests are on the cards in all 54 constituencies in the first phase which would decide the fate of ten ministers. In all, 364 candidates are in the fray in the 54 seats.
Tight security arrangements have been made to ensure peaceful, free and fair polling in all the constituencies spread across north Bengal districts of Cooch Behar, Jalpaiguri, Darjeeling, North Dinjapur, South Dinajpur and Malda.
A total of 12,133 polling centres have been set up in the six districts.
Chief Electoral Officer Sunil Kumar Gupta said central and other security forces have reached the areas going to the polls and started flag march and area domination. Inter-state and international borders have been sealed.
He said 16 polling booths are located in remote hilly terrain in Darjeeling and in Kalimpong and polling personnel had been despatched there on Saturday.
The election is being held in the backdrop of slogans for bringing in political change and witnessed high-voltage campaign.
Congress President Sonia Gandhi and general secretary Rahul Gandhi besides senior party leader and Union Finance Minister Pranab Mukherjee hit the campaign trail to canvas for the alliance candidates.
Blaming the Left Front for Bengal's ''under- development'', Gandhi promised that the Congress-Trinamool alliance would make Bengal an advanced state if voted to power.
During his campaign, Rahul Gandhi criticised the LF for its ''misrule'' and said this election will bring an end to the CPI(M)-led government.
Trinamool Congress supremo Mamata Banerjee toured the entire north Bengal to campaign for alliance.
Chief Minister Buddhadeb Bhattacharjee did not campaign for the Left candidates in north Bengal. Among the Left leaders who canvassed included CPI(M) politburo member Brinda Karat, Sitaram Yechury and state Housing Minister Gautam Deb.
Prominent BJP leaders who took part in electioneering included L K Advani, Gujarat Chief Minister Narendra Modi and Arun Jaitley besides Hema Malini.