
Well, an Al-Qaeda affiliate claimed it
A cassette tape with koran verses was discovered in a truck with spare detonators. And the same group that claimed the Istanbul bomb last Monday claimed this attack in an e-mail to an Arabic newspaper in London. In the mean time, PM Aznar still insists ETA did it, so right now, confusion rules supreme.
It wouldn't be the first time here the far right state-in-the-state brigades tried to steer public opinion by committing terrorist acts and then blame those on militant lefties. The key to their success whas that they had sufficient support within the government, law enforcement and spook agencies that the cover-up worked.
But the scope of this one is such that it would hand Spain to the separatists (not just the Basques) if it becomes clear any part of the government apparatus knew about it, abetted it, or assisted in a cover-up. That doesn't rule it out of course, but it would be the stupidest thing they've ever done.