A three-year-old boy has died after falling out of a roller coaster at a Chicago amusement park, police said.

The boy was sitting near the front of the Python Pit roller coaster at the Go Bananas amusement park when he got underneath the ride's safety bar, Norridge police chief James Jobe said.

He suffered head injuries in what Mr Jobe described as "a tragic accident".

The boy was on the ride with his twin brother when he fell out of the coaster while it was moving, Mr Jobe said.

The Cook County medical examiner's office said the boy died at the park. Police said a state inspector was at the scene.

A spokesman at the amusement park said they are co-operating with investigators.

"We're certainly very sorrowful," he said.

Authorities said they believe the boy met all the requirements for the ride.

The boy was from the southern Chicago suburb of Dolton. His identity has not been released.