Flags flew at half-mast Friday as Norway held the first funerals for victims of the twin attacks a week before, and police said psychiatrists would assess the mental health of Anders Behring Breivik.
The death toll in the July 22 attacks rose to 77 after police released a new list of victims' names.
"The bullets hit our young, but they also struck an entire nation," Prime Minister Jens Stoltenberg said at a commemoration ceremony in the capital, calling the massacre "an attack on democracy."
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Police said prosecutors had appointed two psychiatrists to determine if Behring Breivik, 32, is criminally responsible for the July 22 shooting spree at a youth camp and a car bomb blast in Oslo.
Norway's Foreign Minister Jonas Gahr Stoere attended the first funeral, of Bano Rashid, who was originally from Kurdistan, in the town of Nesodden, near the capital.
Rashid, a Labour Party youth activist among the 69 killed while attending a summer camp on the island of Utoeya, had written frequently about the evils of racism and discrimination.
Her younger sister escaped the massacre on the island, and her mother told NTB: "The answer must not be hatred, but even more love."
Another shooting victim, 19-year-old Ismail Haji Ahmed, was buried at Hamar, in Norway's south-west, TV2 reported.
Self-confessed killer Behring Breivik was driven from Ila high-security prison, where he is being held in solitary confinement, to police headquarters in an armoured car early Friday for further questioning. The windows of the vehicle were covered to prevent photographs.
He admitted carrying out the attacks when questioned last Saturday, but stopped short of entering a guilty plea for actions that his lawyer said he deemed "cruel" but "necessary".
The 1,500-word tract he published on the Internet before the attacks said it was part of a campaign against Muslim immigration to western Europe.
On Monday a judge ordered Behring Breivik held for an initial period of eight weeks, but prosecutors have said it will take months to gather evidence and he will not be brought to trial until next year at the earliest.
In Oslo, Stoltenberg led a minute's silence before delivering a speech to hundreds of members of his governing Labour Party.
The crowd at the ceremony held aloft red roses, the Labour Party emblem, in tribute to the victims.
"Today, it is exactly one week since Norway was struck by evil," the premier said. "Now, the time has come to commemorate those who died."
In "a massacre planned in minute detail and perpetrated in cold blood," the party's youth, including some of its brightest talents, were mowed down "with their lives in front of them. Everything has been taken from them."
Stoltenberg also spoke of the seriously wounded in hospital, and those "who carry invisible scars, but who bleed and who are still bleeding."
Eskil Pedersen, the leader of the party's youth wing, told mourners: "We will not remember our dead with grief, we will remember them with a smile."
Pedersen was one of those caught on the island during the shootings.
Stoltenberg and Olso's Lutheran bishop Ole Christian Kvarme later attended a ceremony at an Oslo mosque, where a prayer of mourning was recited, television pictures showed.
Behring Breivik's lawyer meanwhile told the daily Aftenposten his client had been planning to hit other targets.
"There were several projects of different scale for that Friday," Geir Lippestad was quoted as saying.
"Things happened that day, which I don't want to go into (here), which meant events unfolded differently from what he had planned," Lippestad added.
Police investigator John Frederiksen said dozen sites have been checked but nothing found indicating a further threat.
And Norway's intelligence service, the PST, said Friday there was no reason to raise the alert status measuring the country's threat level.
Having measured the various factors, "... it is not very likely that the attacks are followed by new terrorist attacks," said a statement.
"In all likelihood, the author planned and carried out actions without support," it added.
According to a new police list, last Friday's car bomb killed eight people in Oslo city centre, while 69 people died in the shooting rampage at Utoeya, some 40 kilometres (25 miles) outside the capital. A previous toll had given 68 deaths from the shootings.
Earlier Friday, police said they were no longer searching for missing people.
