Pram rolls in front of oncoming Sydney train, toddler and father killed

A pram carrying twin two-year-old girls rolled into the path of an oncoming train in Sydney on Sunday, police said, in an accident that killed one of the children and the "heroic" father who dashed to their rescue.

One of the little girls survived only "through good luck" after she landed between the rails when the pram fell off a platform at southern Sydney's Carlton railway station, police said.

She was "largely untouched" by the train that apparently passed above her on its way to central Sydney in the early afternoon, police said.

The parents had taken a lift down to the station platform and as they exited, they took "their hands off the pram for a very, very short period of time", New South Wales police superintendent Paul Dunstan said.

"Whether it's a gust of wind or — we're not quite sure — but it appears that the pram has instantly started to roll in the direction of the train lines," he told a news conference.

Police and emergency services arrived within a few minutes of being alerted and were able to see the pram under the train, which had slowed on approach but was not scheduled to stop at the station.

"You could hear crying coming from underneath the train," the police superintendent said.

Though one of the children was unharmed, the other girl and her 40-year-old father had been killed.

"In the face of a terrible, terrible accident, he gave his own life to try and save his children."