At least three Trinamool Congress workers sustained injuries in a blast that took place at their party office in the Uttar Bar area of Bankura district.
After the blast, local residents rushed to the spot and rescued a party worker. He was sent to the Bishnupur district hospital. The police also arrived at the spot to investigate the matter.
Locals alleged that some people were seen making explosives inside the party office before the blast occurred.
The incident comes ahead of the first phase of polling in West Bengal. Elections to the 294-member West Bengal Assembly will be held in eight phases starting from March 27 with the final round of voting taking place on April 29. The counting of votes will take place on May 2.