Police constable Prakash Vir (45), his wife and son died when their motorcycle was hit by a car in Bharatpur district, they said.
The car driver and other passengers fled after the incident leaving the car behind, they said, adding, the car was seized.
In another incident, two senior citizens were killed and 19 persons injured when a truck collided with a jeep in Sirohi district, police said.
Sushiya (70) and Babu Lal (80) died in the mishap, they said.
The injured were rushed to hospital where their condition was stated to be stable, they said.