The incident took place when the party workers took shelter under a tree during thunderstorm.
The injured were rushed to hospital.
The workers were attending a party rally by its National General Secretary Abhishek Banerjee during his two-month-long Jono Sanjog Yatra (mass contact outreach) ahead of the West Bengal Panchayat poll.
"Our hearts go out to those affected by the lightning incident at Indas, " the party tweeted.
"We extend our condolences to the family of the deceased & will do our best to support them, " the party said.
