Norway on Monday reopened its renovated government headquarters in central Oslo, almost 15 years after the buildings there were severely damaged when mass killer Anders Behring Breivik detonated a bomb.

Norwegian Prime Minister Jonas Gahr Store speaks during the official opening of the new government quarter at Hammersborg in Oslo, Norway April 13, 2026. (Photo: AFP)

On July 22, 2011, Breivik set off a bomb in a van near the government complex killing eight people, before gunning down 69 others, mostly teens, at a youth wing summer camp on the island of Utoya.

"In Norwegian history, we talk about the post-war reconstruction, today we mark the rebuilding after terror, which says a great deal about the vulnerability of the modern society we live in," Prime Minister Jonas Gahr Store said.

The government complex was heavily damaged, and some of the buildings could not be used.

The reconstruction started in 2021, and the cost is estimated at over 50 billion kroner ($5.3 billion), according to news agency NTB.

On Monday, the first 2,200 staff from six ministries moved into the complex, which will eventually be the workplace of some 4,100 government workers.

"We must not forget, we must preserve history, honour those we lost, and stand by those who are still marked by terror," Store said.

The new complex also includes a permanent national memorial centre and artwork commemorating the massacre, which Store said would be completed in July.

Anders Behring Breivik is seen partly obscured in the back seat as he arrives in an armoured police vehicle for questioning at the Police HQ in Oslo on July 29, 2011. (Photo: AFP)

Breivik, now aged 47, was in 2012 sentenced to 21 years in prison, Norway's then-harshest sentence which can be extended as long as he is considered a threat to society.

He said he killed his victims because they embraced multiculturalism.