Two trains running on the same track have collided head-on in southern Poland, killing 16 people and injuring 58 in the country's worst train disaster in more than 20 years.

The collision just north of Krakow late on Saturday came after one of the trains ended up on the wrong track. Neighbours in the town of Szczekociny were alerted by what they said sounded like a bomb and rushed to the scene as survivors emerged.

Rescuers worked through the night to recover bodies and help the wounded. Maintenance work was being done on the tracks before the accident, but officials said it was too early to determine the cause of the disaster.

A woman living in a house about 200m from the site of the accident said she was standing at her window when the two trains collided, creating a "terrible, terrible noise like a bomb going off".

"So I ran out of the house, and on one side I saw train lights and one the other side I saw train lights, and in the middle sparks," Anna Sap said. "People from the train starting crying, 'Help, help!' So we and the neighbors ran to them. Some of them smashed windows to let them out."

An unnamed passenger interviewed on the all-news station TVN24 described the moment of the collision. "I hit the person in front of me. The lights went out. Everything flew," he said. "We flew over the compartment like bags. We could hear screams. We prayed."

The US consulate in Krakow said an American woman was among the dead and her family had been informed. Spokesman Benjamin Ousley said he could give no more information.

The country's prime minister, Donald Tusk, earlier said earlier that several of the passengers were foreigners, including people from Ukraine, Spain and France, but none of them were among the dead or mostly seriously injured.

"This is our most tragic train disaster in many, many years," Tusk said. "It's a very, very sad day and night in the history of Polish railways and for all of us."

President Bronislaw Komorowski visited the site on Sunday, saying that when the rescue efforts were over he would make an announcement about a period of national mourning.

Rafal Krupa, a council member in the nearby town of Zawiercie, said emergency workers got to the site as quickly as possible, but that in the first moments it was difficult for them to determine where the crash had occurred. Passengers on the train "began calling in to the emergency services but they weren't really aware of where they were," he said.

A doctor in one of the hospitals, Szymon Nowak, said many of the injured were in a serious condition, with some in artificially induced comas. The trains had capacity for 350 passengers but it was not clear how many people were actually on board.

The accident comes three months before millions of football fans begin crisscrossing the country, many of them by train, to watch matches in the Euro 2012 championships, which is being co-hosted by Ukraine.

Prosecutors have opened an investigation into how the train came to be on the wrong track, but officials said it was too soon to draw any conclusions. One train was travelling from the eastern city of Przemysl to Warsaw, while the one on the wrong track was heading south from Warsaw to Krakow.

Germany's foreign minister, Guido Westerwelle, expressed his nation's condolences to the victims' families and wished the injured a swift recovery.
"It is with horror that I learned about the grave train accident in Poland that killed numerous people and injured many others," Westerwelle said. "Our deepest compassion and our condolences go to our Polish friends."

The crash was Poland's worst rail accident since 1990, when 16 people were killed in a collision involving two trains in the Warsaw suburb of Ursus. The country's worst train crash since the second world war dates back to 1980, when a freight train collided with a passenger train near Otloczyn, killing 65 people.