(Updates death count, adds witnesses, description of crash site)
MADRID, July 24 (Reuters) - At least 20 people were killed when a train derailed outside the northern Spanish city of Santiago de Compostela on Wednesday, state media and witnesses said.
Train wagons lay on their sides with smoke billowing from the wreckage, photographs published on the Voz de Galicia newspaper website showed.
"It was going so quickly ... It seems that on a curve the train started to twist, and the wagons piled up one on top of the other," passenger Ricardo Montesco told Cadena Ser radio station.
"A lot of people were squashed on the bottom. We tried to squeeze out of the bottom of the wagons to get out and we realised the train was burning ... I was in the second wagon and there was fire ... I saw corpses," he added.
Another witness told the station they had heard an explosion before seeing the derailed train.
Galician TV and state radio reported at least 20 people had died, citing witnesses.
A spokesman for the regional government's office confirmed there had been a train accident, but said no further details were available.
Emergency services and police were not immediately available for comment.
Santiago de Compostela, the birthplace of Spanish Prime Minister Mariano Rajoy, is best known as the destination of an ancient Catholic pilgrimage route. (Reporting By Inmaculada Sanz and Sonya Dowsett; Editing by Sarah White and Andrew Heavens)
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