The explosion occurred at a local club in Katwa town, about 160 km north of Kolkata, where a huge number of crude bombs and other explosives were found stored illegally, the police added.
"It was a huge explosion. The entire area shook with the impact and was completely covered in smoke," a local resident said.
The locals also said that the club got completely flattened and its roof was bloown away.
"We came out hearing the explosion and saw the club building completely demolished. The elderly man, who was sitting by the club, died on the spot," another local said.
The police reached the spot and recovered plenty of fresh crude bombs among other explosives.
"We received complaints that crude bombs were made and stored inside the local club. Further investigation is on," Bardhaman district's Additional Superintendent of Police (Rural) Raj Narayan Mukherjee said.