Here are the 10 latest developments in this story:
Clashes reportedly began after an argument over setting up of party booth near a polling station. The Trinamool Congress insists BJP workers set up their booth at a spot that it had already identified for itself. Three people were injured in the scuffle that followed and were taken to a hospital, reports news agency ANI.
Over 1.2 crore voters will decide the fate of 383 candidates in six districts in north Bengal - Alipurduar, Jalpaiguri, North Dinajpur, Darjeeling, South Dinajpur and Malda - and one in south Bengal.
The only south Bengal district with 11 constituencies that went to the polls in this phase is Birbhum. Seven constituencies here - Dubrajpur, Suri, Nalhati, Rampurhat, Sainthia, Hansan and Murarai - have been declared Left-wing extremism affected.
The Trinamool is contesting in 55 seats, BJP 53, Congress 23, Left Front 34, GJM three. In the 2011 assembly polls, then allies Trinamool and the Congress had claimed 18 seats each, while the Left Front could only get 15. Among the Left front partners, the Communist Party of India-Marxist, the Revolutionary Socialist Party and the All India Forward Bloc won six, five and four seats respectively. The Gorkha Janmukti Morcha triumphed in three and independents in two seats.
On April 14, the Election Commission had issued a show cause notice to Chief Minister Mamata Banerjee for violating the model code of conduct. Reacting to the notice, Ms Banerjee had dared the Election Commission to take action against her and said people of the state would "showcause" it on May 19, the day of the result.
In Darjeeling's Siliguri, former Indian football captain and Trinamool nominee Baichung Bhutia is pitted against former state minister and CPI-M heavyweight Asok Bhattacharya.
Eyes will also be on Sujapur in Malda where two relatives of late Congress stalwart ABA Ghani Khan Choudhury -- affectionately called Barkatda -- are contesting against each other.
Mr Choudhury's younger brother Abu Nasar Khan Choudhury, in the fray as the Trinamool nominee, is contesting against his nephew Isha Khan Choudhury, representing the Congress.
Among other notable candidates are state ministers Gautam Deb (Dabgram-Pulbari), Krishnendu Narayan Choudhury (English Bazar), Sabitri Mitra (Manikchak) -- all from Trinamool Congress, and BJP's actress candidate Locket Chatterjee (Mayureswar).
So far, voters in 49 of the total 294 constituencies have voted on two dates -- April 4 and 11 - in the first phase. West Bengal is having a staggered six-phase election. Polling for the remaining phases will be held on April 21, 25, 30 and May 5.
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