OSLO (AFP) -- The lawyer for the Norwegian gunman who has claimed responsibility for killing 76 people in twin attacks last week said Tuesday that everything about his client's case indicates he is "insane.” 

  "This whole case indicates that he's insane," Geir Lippestad told journalists of Anders Behring Breivik, adding that a medical evaluation would take place to establish his psychiatric condition.

   "He believes that he's in a war and he believes that when you're in a war you can do things like that without pleading guilty," the lawyer said of the 32-year-old Norwegian who claims to be trying to bring about an anti-Muslim revolution.

   Asked about the implications of his client being adjudged medically insane after blowing up the government centre in Oslo and shooting dead 68 people on a nearby island, Lippestad said: "He can't be punished in a jail."

   Paving the way for a defence that could see his client escape prison, after medical experts acceptable to the prosecution are found, Lippestad said Behring Breivik "has a view on reality that is very, very difficult to explain."

   He said his client used drugs to make himself "strong" going into Friday's rampage.

   "He thought he'd be killed after the bombing, after the action on the island, and he also thought he'd be killed at trial," Lippestad said.

   In fact, "he was a little bit surprised that he succeeded, that in his mind he succeeded," Lippestad added.

   Asked whether Behring Breivik had shown any empathy for his mainly young victims, Lippestad said: "No."

   Behring Breivik wrote and published a 1,500-page manifesto immediately before starting his bombing and shooting spree.

   "He believes this war will continue for 60 years and in 60 years this war will be won," Lippestad said of the events he believes he has triggered, preparations for which are painstakingly chronicled in the tract.

   Authorities said earlier they were considering charging Behring Breivik with crimes against humanity over the massacre in Norway as the government leapt to the defence of the police over its handling of the tragedy.

   Faced with the worst crimes on its territory since World War II, many in Norway have been dismayed by the prospect that the perpetrator could serve just

21 years behind bars -- the maximum sentence allowed for the terrorism charges that Behring Breivik currently faces.

   But prosecutor Christian Hatlo told the Aftenposten newspaper that police are now envisaging charging him with crimes against humanity for the bombing of Oslo's government district and a shooting bloodbath on a nearby island.

   "Police have so far cited... the law on terrorism but seeking other charges has not been excluded," police spokesman Sturla Henreiksboe told AFP.

   "No final decision has yet been taken," he said.

   Behring Breivik admitted carrying out the attacks at his first court appearance on Monday when he was remanded in custody for eight weeks.

   He says he was on a Crusade to save Norway and Western Europe from a Muslim invasion and that the attacks targeting the Labor Party-led government and its youth wing were "cruel" but "necessary.”

   Police said they would start releasing the names of those killed, many of them children, probably later on Tuesday.

   The police have come in for heavy criticism over the time it took them to reach Utoeya island where Behring Breivik shot dead 68 of his victims in a spree that lasted around 90 minutes.

   It also emerged on Monday that police investigated Behring Breivik in March for a purchase of chemicals, but the probe was dropped.

   In a press conference on Tuesday, Norway's Justice Minister Knut Storberget rejected criticism of a delay in police getting to the Utoeya island, saying the force had "delivered extremely well" with "fantastic" work.

   United in grief, more than 100,000 flower-carrying Norwegians thronged central Oslo on Monday evening in a vigil for the victims.

   Prime Minister Jens Stoltenberg admitted the country would be changed permanently by the attacks, but vowed to ensure it remains an open society.

   He told the grimly defiant crowd massed in the city centre: "Evil can kill a person but it cannot kill a people."

   The manifesto saw Behring Breivik boast that he was one of up to 80 "solo martyr cells" recruited across Western Europe to topple governments tolerant of Islam.

   Police are probing his claim that he is part of a network with more active cells.

   "The police are investigating all leads and all information pertaining to (Behrin Breivik's) involvement and looking into the possibility that he may have had collaborators," Henriksboe told AFP.

   "At this point we cannot comment on the details of the investigation."