They might very well be Turkish. Internet is full of these "script kiddies". I administer servers for a living and god knows how many times my public servers come under attack (sometimes several hundered/day). From the looks of it, seems like buch of kids trying to make a name for themselves. I wouldn't look for any kind of political motivation under it.
That being said, I am kind of impressed they were able deface an official google website. Most probably they didn't hack the google servers but some kind of DNS poisoning attack.