It was coordinated over several distant places, and it knew what, where, when, and how to strike (suggesting an inside job), so the timing with the Olympics wasn't a coincidence, especially with the heavy reliance and messaging on transports.
No one has made any claim, but the government is saying it's the same methods from the fAr LeFt because of the required knowledge.
Not that I was involved or whatever. But how can someone say they had a method when basically it was just a group of dickheads grabbing a map and saying go here or here and here then lighting the place up? Im from America usually something like this is way more convuleted.