Polling began at 7 am on Thursday for the by-election to the Bhabanipur seat, where West Bengal Chief Minister Mamata Banerjee is contesting, and two other constituencies amid tight security and stringent Covid-19 measures, officials said. The bypolls are being held in south Kolkata's Bhabanipur, besides Jangipur and Samserganj seats in Murshidabad district. A total 6,97,164