The claim comes amid a series of revelations about the killings, with police admitting they could have taken a much quicker route to the island.
Oslo police chief of staff Johan Fredriksen also conceded officers could have called on a rescue helicopter.
But he denied claims the aircraft could have transported snipers in time to make a difference or that it would have ensured a faster arrival on the island for specialist terror police.
Oslo police lawyer Christian Hatlo said Breivik had made references to having filmed his entire 72-minute killing spree.
The shootings came just hours after a bomb blast in the capital he is also suspected of, which left 10 people dead.
"We have information from his manifesto and from earlier interrogations indicating that he did have a camera," Mr Hatlo said.
He said evidence at Breivik's home suggested he had a camera and had intended to film the attacks.
"We are looking for his camera but have not found anything so far," he said. Read More