Four years after a right-wing extremist killed 77 people in Norway, Prime Minister Erna Solberg says July 22, 2011, will always remain a dark day in the Scandinavian country's history.

At a wreath-laying ceremony outside the new July 22 Center, Solberg said Wednesday the victims will never be forgotten and that "we remember them with love."

Anders Behring Breivik, serving a 21-year prison sentence, confessed to the bomb attack at government headquarters that killed eight people and a shooting rampage at a youth camp on Utoya island off the capital, Oslo, where he murdered 69 others.

Several ceremonies were to be held throughout Wednesday, also attended by NATO Secretary General Jens Stoltenberg who was Norway's prime minister at the time of the attacks.