Turkish Airlines told Sky News the girl became ill during the flight on Sunday and cabin crew asked over the PA system if there was a doctor on board.

The captain of the plane "immediately diverted to Budapest" and a doctor on the flight attended to the girl, the company added.

After the plane made an emergency landing at Budapest International Airport, "medical teams boarded the aircraft for further treatment but despite all efforts, [the] passenger couldn't be saved", Turkish Airlines said.

"We offer our heartfelt condolences to the family and loved ones and share their pain," the company added.

The plane continued its journey to New York after a four-and-a-half hour delay.

Some reports said the child who died was a boy but Turkish Airlines confirmed the passenger was a girl.

The cause of death has not been revealed.