The attack traumatized Spain on the eve of an election.
The campaign was largely dominated by separatist tensions in regions like the Basque country, with both the ruling conservative Popular Party and the opposition Socialists ruling out talks with ETA.
But the Socialists came in for withering criticism because a politician linked to the Socialist-run government in the Catalonia region, which also has separatist sentiment, admitted meeting with ETA members in France in January.
Shards of twisted metal were scattered by rails in the Atocha station at the spot where an explosion severed a train in two.
"I saw many things explode in the air, I don't know, it was horrible," said Juani Fernandez, 50, who was on the platform.
"People started to scream and run, some bumping into each other and as we ran there was another explosion. I saw people with blood pouring from them, people on the ground," Fernandez said.
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