AT least 25 people have been killed and dozens are injured after two passenger trains collided head-on at high speed in southern Italy, sending debris flying into surrounding olive groves.

Three carriages were torn apart by the violence of the impact after the two trains hit each other while travelling down the same stretch of track linking the small towns of Corato and Andria in the southeastern Puglia region.

Rescue operators raised the death toll to 25 after a day of frantic rescue operations, and warned that it could climb higher as some of the 50 injured were in serious condition.

Australia’s Department of Foreign Affairs says embassy officials in Rome are trying to determine if any Australians were caught up in the disaster.

There was no immediate indication of what had caused one of Italy’s worst train disasters in recent years, but the government promised a full and swift investigation.

“I found a horrific terrifying scene,” said one of the first policemen to arrive on the crash scene. “There were dead people, there were people screaming for help, stuck in the wreckage, there were passengers crying their eyes out, totally shattered .

 It was the worst thing I have ever seen.”