Purulia superintendent of police Neelkanta Sudhir Kumar said four workers were struck by lightning when they were constructing a building for ICDS at Puncha, about 32 km from Purulia town.
Three of them were killed on the spot and another was critically injured. He was rushed to the hospital, Kumar said, adding, all four hailed from nearby villages.
In the second incident, two persons were killed due to lightning during torrential downpour at Udaynarayanpur in Howrah district.
The others escaped unhurt and the madrasa building was partly damaged, they added.