Fifteen people were killed when two passenger trains collided head-on in southern Poland late Saturday in the country's worst train crash in more than 20 years.

The two trains carrying an estimated 350 passengers were travelling at high speed on the same track when they crashed in a rural area near the town of Szczechociny. At least 56 people were injured, police said.

The battered locomotive of one of the trains had jack-knifed upwards from the force of the crash. Several cars had derailed and some were lying on their sides.

This certainly is the most tragic train catastrophe in our history in many, many years, said Prime Minister Donald Tusk, who arrived at the site of the crash with several other government officials early Sunday.

Rescuers said they had pulled 14 bodies from the twisted wreckage. One body found by sniffer dogs inside a mangled train car remained trapped and could only be removed with the help of heavy equipment.

There was no braking, only the crash, and the lights went out, people were screaming, passenger Dariusz Wisniewski told a local television station. When we got out we saw bodies and wounded all over, as well as the twisted wreckage. I had never seen anything like it.

President Bronislaw Komorowski visited survivors at a hospital and was headed to the crash site.

Tusk said it was too early to speculate about the cause of the collision, but added that human error could not be ruled out.

Authorities were opening an investigation.

The fate of the two drivers was not immediately known as the authorities were still identifying the dead bodies.

More than 350 firefighters rushed to the scene, but had to carry their equipment by hand because the trains collided in the middle of a field crossed only by the train tracks.

In the hours following the 9.00 p.m. (2000 GMT) collision, they searched the wreck and pried out many of the survivors. The injured were taken to hospitals in the region by helicopter and ambulance.

Among the passengers were several Ukrainians along with French and Spanish citizens. None of them were hospitalised.

One of the trains had been going from Warsaw to Krakow and the other from the city of Przemysl to the capital.

The wreckage on one of Poland's most heavily used train routes was causing heavy delays Sunday.

(Additional reporting by Piotr Pilat and Rob Strybel; Writing by Chris Borowski; Editing by Myra MacDonald and Alessandra Rizzo)