Just because the Jihad websites are excited about the attack doesn't mean they were conducted by Islamists. They may have been two separate groups for each attack with an unlikely synchronization in timing, or both attacks may have been conducted by domestic political extremists. Too early to say at this point. First reports are almost always incorrect.

http://news.yahoo.com/undetonated-ex...213754348.html

Undetonated explosives were found on an island where a gunman killed at least 10 people at a youth camp near Oslo, Norwegian police said on Friday.
Explosives were found on the island," deputy Oslo police chief Sveining Sponheim told reporters. He said a man detained by police was aged 32 and "ethnic Norwegian."