An electorate of 1.26 crore will decide the fate of 366 candidates, including several ministers, in 15,711 polling stations.
Bihar's Chief Electoral Officer Sudhir Kumar Rakesh will be the Special Observer for the fourth phase of the polls.
The constituencies going to polls during this phase include Nandigram and Singur which changed the political scene in the state in the last few years.
There are 16 seats each in Howrah and East Midnapur districts, 18 in Hooghly district and 13 in Burdwan.
CPI(M) heavyweight and Industries Minister Nirupam Sen is pitted against retired professor of Burdwan University Rabiranjan Chattopadhyay of Trinamool Congress from Burdwan South constituency.
Other ministers from the CPI(M) are Higher Education Minister Sudarshan Roychowdhury, Food Processing Minister Mohanta Chatterjee, Minister of State for Information and Culture Soumendranath Bera, Technical Education Minister Chakradhar Maikap.
Agriculture Minister Naren Dey belonging to Forward Bloc and Fire Services Minister Pratim Chatterjee belonging to Marxist Forward Bloc are also contesting.
Trinamool Congress has fielded former IPS officers Rachpal Singh, H A Sawfi and Sultan Singh in this phase.
The state has already witnessed three phases of the polls on Apr 18, 23 and 27. The fifth and sixth phases would be held on May 7 and May 10 respectively.