OSLO — The Norwegian man charged Saturday with a pair of attacks in Oslo that killed at least 92 people left behind a detailed manifesto outlining his preparations and calling for a Christian war to defend Europe against the threat of Muslim domination, according to Norwegian and American officials familiar with the investigation.

As stunned Norwegians grappled with the deadliest attack in the country since World War II, a portrait began to emerge of the suspect, Anders Behring Breivik, 32. The police identified him as a right-wing fundamentalist Christian, while acquaintances described him as a gun-loving Norwegian obsessed with what he saw as the threats of multiculturalism and Muslim immigration.

“We are not sure whether he was alone or had help,” a police official, Roger Andresen, said at a televised news conference. “What we know is that he is right wing and a Christian fundamentalist.”

In the 1,500-page manifesto, posted on the Web hours before the attacks, Mr. Breivik recorded a day-by-day diary of months of planning for the attacks, and claimed to be part of a small group that intended to “seize political and military control of Western European countries and implement a cultural conservative political agenda.”

He predicted a conflagration that would kill or injure more than a million people, adding, “The time for dialogue is over. We gave peace a chance. The time for armed resistance has come.”

The manifesto was signed Andrew Berwick, an Anglicized version of his name. A former American government official briefed on the case said investigators believed the manifesto was Mr. Breivik’s work.

The manifesto, entitled “2083: A European Declaration of Independence,” equates liberalism and multiculturalism with “cultural Marxism,” which the document says is destroying European Christian civilization.