Right, they said it. Some security wonk or another. "Looks like Al Qaeda" (ETA 13:56 CEST - Al Qaeda claims responsibility) And cited similarities to Madrid. And the IRA has never carried out anything of this scale without prior warning.
THE TOP OF THAT BUS WAS TOTALLY BLOWN OFF I fucking hate being powerless and able only to watch and cry and just look at the people on the pavement and the walking wounded and there is NOTHING I CAN DO.
See caribbeanblue's post for more links.
ETA: Confirmed at least
ETA2: France upped security measures as a result of the London blasts, other European capitals reported to be following suit.
ETA4.5: Local news just confirmed that the bomb threats were a hoax. WTF, fellow citizens of fair Budapest. WTF.
ETA6: xylodemon has a post where you can vent, hang out, chat, whatever.
Blair: "it's reasonably clear that there have been a series of terrorist attacks"