Police spokeswoman Monika Schindlova said: “The collision killed three people, the driver of a car and two people in the bus.”
Several injured passengers were still trapped inside the bus, which struck a tree after veering off the road.
Police also said 45 other people were injured, including five in a serious condition, 10 moderately and the remainder only lightly.
Rescue workers managed to remove several injured passengers trapped inside the bus, which struck a tree after veering off the road.
An investigation has been launched to establish the cause of the accident.
Rescue service spokeswoman Jana Postova said: ”Two children sustained serious head injuries and were put on artificial ventilation and into artificial comas.”
The damaged bus belongs to the private Arriva company and was the link between the 6th district of Prague and the village of Holubice, north-west of the Czech capital.
The accident happened near the town of Bolzano where the bus unexpectedly swerved off the road and crashed in a field.
The driver was killed on impact, 20 tourists were taken for treatment to nearby hospitals, some of them with serious injuries.
More to follow.