OSLO - Radical Islam remains the most serious threat faced by Norway despite the attacks by an Islamophobe extremist who killed 77 people last summer, the chief of the security police said on Tuesday.Janne Kristiansen, head of Norway's Police Security Service, said her agency would focus on broad-based dangers from home-grown Islamic extremism even though threats against public officials have risen since the July attacks, which targeted Norway's left wing.RELATED:Norwegian mass killer criminally insane, say expertsEditorial: Norway’s challenge"In recent years we have seen a development in which (Muslim) people raised in Norway become radicalized, and for whom Norway and Norwegian society are the enemy," she told a news conference. "These people have a lot of contact with extreme Islamists abroad. They travel to training camps in conflict areas and they travel to participate in armed combat before returning to Norway."Responding to critics who have said the police are neglecting the threat from right-wing militants like Anders Behring Breivik, who admitted carrying out the July 22 attacks, she said the threat they represent is far smaller."The number of violent right-wing extremists is still low," she said.She added that a rising tide of hate-filled debate on Internet sites brought "a significant source of uncertainty" to her overall threat assessment.Politicians and their parties, she said, have seen a rise in the number and severity of threats since the July attacks and should expect the problem to continue when Breivik's high-profile trial begins on April 16. She did not specify whether the proliferation of political threats stemmed from right-wing environments.Breivik has told police he bombed government headquarters in Oslo, killing eight people, before shooting 69 more at an island summer camp for Labour Party youth members - acts designed to punish what he called pro-immigration "traitors."