Prime Minister Jens Stoltenberg urged parliament on Monday to preserve the democratic values of Norway as public pressure grew for stiffer sentences for serious crimes after an anti-immigration zealot's bloody rampage.

Norway's Prime Minister Jens Stoltenberg (R) arrives with his wife Ingrid Schulerud for the funeral ceremony of Mona Abdninur, 18, in Hoeybraeten, near Oslo August 2, 2011. Abdninur was one of the 77 people massacred in attacks of the anti-Islam zealot Anders Behring Breivik in July.[Photo/Agencies]

In a poll of nearly 1,300 people taken six days after the attacks that left Norwegians devastated, 65.5 percent said penalties were "too low" and 23.8 percent were happy with them, the Verdens Gang paper reported. More than half said their view had hardened since the mayhem that claimed 77 lives.

Anders Behring Breivik, 32, who confessed to the July 22 bombing in Oslo and the cold-blooded shootings on a nearby island, was charged by police with terrorism which carries a sentence of up to 21 years. This can be extended.

The case has caused public debate about the state of society in affluent Norway with politicians and voters scrutinizing crime and punishment as well as immigration and tolerance.

"We must listen and have a debate, while not drawing hasty conclusions ... It's important that policy isn't shaped in a state of panic," said Justice Minister Knut Storberget, who also told VG he was "not surprised" by calls for stricter laws.

At a special session of parliament Stoltenberg on Monday commended Norwegians for their self-control in the 10 days since the worst attack on the normally peaceful Nordic nation since World War Two, saying they had renewed their commitment to an open society.

The broader aim of Breivik's attacks was to save Europe from "cultural Marxism" and "Muslim invasion", according to a manifesto published hours before the killings. The majority of the victims were teenagers at a Labour Party youth summer camp.

Many Norwegians have expressed relief that Breivik seems to have been a lone, home-grown fanatic rather than an envoy of a broader militant group. Many compare him to Timothy McVeigh who killed 168 people with a truck bomb in Oklahoma City in 1995.

"Shock, fear and despair"

"Everyone had to choose their own path in a landscape filled by shock, fear and despair," Stoltenberg said. "But the Norwegian people found their way home again."

Stoltenberg said many Norwegians may now wish they had positioned themselves differently on issues like immigration and tolerance but he urged parliamentarians to steer clear of measures that would curtail the country's democratic freedoms.

"I would like to ask from this podium that we avoid starting a witch-hunt on expression," he said.

The government also said it would hold a national ceremony of remembrance in Oslo on August 21, inviting relatives, survivors and rescue workers to the event.

Police said more than 200 witnesses have so far been interviewed and that Breivik himself faced more questioning this week that will be "more confrontational" than previous sessions.

"It's way too soon to say anything about whether he is insane or sane," said police prosecutor Paal-Fredrik Hjort Kragy, adding: "That is for the psychologists to decide and we will await their investigation."

If deemed a continuing danger to society Breivik could face an additional series of five-year protective custody sentences, and some have called for charges related to crimes against humanity that could give an initial sentence of up to 30 years.

Researchers doubt Breivik's claims that he is part of a wider far-right network of anti-Islam "crusaders", seeing them as empty bragging by a psychopathic fantasist who has written that exaggeration is a way to sow confusion among investigators.