The first incident took place near Mahua village yesterday when a car lost control and hit a tree killing Omi (7) and injuring his father K K Singh, mother Priyanka and driver Amarm, they said.
The injured were taken to a hospital, where their condition was stated to be stable, the police said.
In another incident in Palra village in Chilla area, one Arjun Sahu (8) was killed after being hit by a truck while crossing a road, they said.