At least 15 people have been killed and 50 others injured when two passenger trains collided head-on in southern Poland.

The accident occurred on Saturday evening on the Warsaw-Krakow mainline in a rural area near the town of Szczekociny, according to Polish TV.

The two trains carrying an estimated 350 passengers were heading in opposite directions on the same track when they crashed at high speed at 21:00 local time (20:00 GMT), according to Poland's PKP railways.

One train was en route to the southern city of Krakow from the capital Warsaw, while the other was travelling to the capital from the south-eastern city of Przemysl.

'Worst catastrophe'

Donald Tusk, the Polish prime minister, arrived at the scene early on Sunday morning, with three other cabinet ministers.

"This is the worst catastrophe in years," Donald Tusk, Poland's prime minister, said upon his arrival at the scene.

Ukrainian nationals were reported to be among the injured, while French and Spanish citizens were also on the trains, but apparently not injured in the crash.

An investigation was swiftly launched into the reasons behind the fatal crash as the rescue operations continued in the early hours.

Images of the wreckage broadcast by the TVN24 commercial news channel showed tonnes of mangled metal, with reports indicating that three carriages had jumped the tracks along with the locomotives from both trains.

"We heard a deafening noise and we were hurled out of our seats," an unnamed survivor told the PAP Polish news agency.

"We saw crushed bodies pinned beneath seats and we saw parts of bodies inside and outside the train wagons," the survivor said.

'Challenging' rescue efforts

"It was terrifying. The scale of destruction is huge," one of the first firemen on the scene told the PAP.

Another survivor told the TVN24 news channel of dead bodies as well as people still alive but trapped under twisted metal.

Fireman Grzegorz Widawski described the conditions at the crash site as "very challenging."

"The wagons are in very bad shape and it's difficult to get to the people trapped inside," he told the PAP.

A total 450 firemen and 100 policemen were involved in the rescue efforts, emergency response authorities said.

Saturday's accident is the worst rail catastrophe in Poland since 1990, when 16 people were killed in a collision between two trains in the Warsaw suburb of Ursus.

The country's worst train accident occurred in 1980 in Otoczyn, near the northern city of Torun when 67 people died and 62 were injured in a collision between a passenger and a freight train.