The incident occurred at Hariharpara village under Krishnadebpur panchayat in Kalna I block this afternoon.
After hearing a loud explosion, local people arrived at the spot and found three wounded men in the under- construction house of Babu Mondal, local leader of Trinamool Congress' trade union wing.
The three - identified as Tanmay Malik, Uday Barik and Nabakumar Bag - were taken to Kalna Sub-divisional Hospital where their condition was stated to be serious.