Police are initially seeking to hold Philip Manshaus in custody for four weeks on suspicion of murder and breach of anti-terrorism law.
Manshaus, who briefly smiled at photographers, does not admit to any crime, his lawyer said earlier.
Manshaus, a 21-year-old man living near the al-Noor Islamic Centre just outside the Norwegian capital, had expressed far-right, anti-immigrant views before the attack, police said earlier.
Online postings under Manshaus’ name, made shortly before the attack, expressed admiration for the massacre at two New Zealand mosques in March by a suspected right-wing extremist, in which more than 50 people were killed.
Reuters could not independently verify that the postings were made by Philip Manshaus.
He was overpowered by a 65-year old member of the mosque, who managed to wrestle away his guns, preventing anyone from getting shot.
The court hearing will not be open to the public.
A guilty verdict on charges of breaching anti-terrorism laws can carry a sentence of up to 21 years in prison, as can the killing of the suspect’s 17-year old stepsister, according to Norwegian sentencing guidelines.
(Production: Ilze Filks)