As they informed us with one message, αυτή τη στιγμή πραγματοποιείται επίθεση DDoS σε δύο κυβερνητικές ιστοσελίδες, πού όπως δείχνουν, κατά τη στιγμή της συγγραφής αυτού του κειμένου παραμένουν offline.
Sites are in the domains primeminister.gov.gr and startupgreece.gov.gr.
Both are subdomains of gov.gr where almost all government websites are hosted.
According to the Powerful Greek Army, the DDoS attack was carried out (and apparently continues to be carried out) in collaboration with Hellenic hacking teams with them @PhantomNations
Below you can see the screenshots shown by DDoS 
In our question, why did PGA respond to these attacks:
To see how good protection such popular government sites have, they have not at all.
And a screenshot from startupgreece
