An FIR was registered against BJP leader Mukul Roy and three others on Sunday, a day after Trinamool Congress MLA Satyajit Biswas from Krishnagunj in Nadia district was shot dead by unidentified assailants. Of the four booked, two have been arrested, police said.

Biswas was shot dead during a Saraswati Puja celebration in the area. The assailants pumped bullets into Biswas after he disembarked from the stage where a cultural programme was taking place. He was immediately taken to a local hospital where doctors announced him "brought dead".

State minister Ratna Ghosh and Gourishankar Dutta, president of Nadia Trinamool Congress unit, luckily survived the attack as they left the spot minutes before the firing. Three people were detained in connection with the shooting on Saturday.

“We have detained three persons in this connection. We have recovered the country made revolver which was used to kill the MLA. Preliminary investigation revealed that he was shot dead from behind. It’s a pre-planned murder,” said Rupesh Kumar, Superintendent of Police, Nadia district.

Nadia is a district bordering Bangladesh and the BJP has made significant political inroads in recent times. Satyajit Biswas was involved with the Matua community, which has remained politically sensitive both for the TMC and the BJP.

Gourishankar Dutta has blamed the BJP and followers of Mukul Roy for this murder.

“Satyajit was popular among the Matua community where BJP was trying to make its presence. Recently, they brought Prime Minister Narendra Modi for his speech at Thakurnagar in Bongaon Lok Sabha constituency. It was Satyajit who managed to convince people that the BJP is trying to fool them just because of votes. It was because of his growing popularity, BJP eliminated him,” Dutta alleged.

However, BJP state president Dilip Ghosh has denied the charges and blamed the factional fight in the TMC. He further demanded that culprits should be identified immediately.

Dilip Ghosh, while speaking to CNN-News18 over the phone, said that the CBI should look into the case of the TMC MLA murder as the BJP doesn’t have faith in West Bengal police.

The case has been transferred to CID. A team of CID officers has already rushed to Nadia.

"We offer our deepest condolences to the family and friends of TMC MLA Satyajit Biswas who was murdered in tragic circumstances. Culprits should be brought to justice," tweeted Bengal BJP.

Biswas, a young and popular leader, had recently got married.

In December last year, three people, including a TMC member, were killed when unknown assailants fired upon the vehicle of party MLA Biswanath Das at a petrol pump in Joynagar in 24 South Parganas district. The MLA was not in the vehicle at the time of the attack.