“Mohammad Attaulla Hossain (28) died after he suffered 80 per cent burns. Two others are undergoing treatment at SSKM hospital. One of them is very critical,” said a police officer.

“We are investigating if bombs were being assembled for unleashing violence during polls,” South 24-Parganas SP L N Meena said.

A police officer said the three were CPM supporters and Attaulla had several criminal cases registered against him.

While local CPM councillor Shyamsundar Bera claimed they were attacked by some miscreants with bombs, Meena said, “We have found splinters and other material used to make bombs. The bomb exploded inside the house where it was being made.”

Meanwhile, ahead of the civic polls, the police have rounded up five strongmen from north and central Kolkata.