The mishap occurred on the Rohtak-Panipat railway lines, they added.
The deceased have been identified as Sushma (50), Yatish (22) and Meena (28), all from Karnal.
Meanwhile, the two-and-a-half-year-old injured girl Pari has been admitted in PGIMS hospital where her condition was stated as critical.
According to an eyewitness, the accident was so severe that the train dragged the car for several meters.
"The car had converted into a mass of scrap till the train came to a stop," he said.
The victims were retrieved from the car by villagers who rushed to spot immediately after the accident.
The family was coming to Rohtak from Karnal to meet their relatives when the accident took place, police said.
