The attacks, which right-winger Anders Behring Breivik has admitted, traumatised normally peaceful Norway. He is facing terrorism charges and police are considering also charging him with crimes against humanity.
The bomb damaged the office of the Administration and Church Affairs Minister, Rigmor Aasrud, as well as the prime minister's office and other buildings.
Police are still searching for people reported as missing after last week's bomb attack and shootings on an island, and the process of identifying those killed is continuing.
Anders Breivik's lawyer says it's too early to say whether his client will plead insanity at his trial, even though he thinks the loner and computer games enthusiast is probably a madman.
A medical evaluation will be carried out to establish his psychiatric condition.
The police believe he acted alone, although he has stated that he belonged to a radical network with two cells in Norway and more abroad.
Security police say they don't have any evidence of the cells, either in Norway or in Britain.
Justice Minister Knut Storberget deflected criticism that police had reacted too slowly to the shooting massacre, hailing as "fantastic" their work after the attacks.
"It is very important that we have an open and critical approach...but there is a time for everything," Mr Storberget told reporters after talks with Oslo's police chief.
The gunman killed 68 people at a Labour Party youth camp on Utoeya island and eight in an earlier bombing of Oslo's government district. An armed SWAT team took more than an hour to reach the island.
Meanwhile, police say they have found and detonated a cache of explosives at a farm rented by Anders Breivik. They refused, however, to disclose the quantity or nature of the explosives.