Hundreds of political youth are joining a summer camp on Utoya for the first time since a right-wing extremist killed 69 people in a murderous rampage on the Norwegian island four years ago.

Survivor Sverre Outhouse says he's "been through a lot" since he lost close friends in the horrific attack on July 22, 2011, but that it was time to return and have a "great time" with friends.

The murderous rampage of the self-styled "militant nationalist" Anders Behring Breivik traumatized the small Scandinavian nation, with about one in four people affected through connections with family, friends or acquaintances of the victims.

More than 1,000 youth have enrolled for a weekend of political seminars and social activities, organized by the left-wing Labour Party's youth wing that owns the island.