Norwegian police responded as quickly as possible when an anti-Islamic gunman set off a bomb in Oslo and shot dead dozens of teenagers at a summer camp in July, the head of an internal police commission assessing the response said on Friday.

Victims' families have strongly criticised police for not reacting faster to reports that the gunman, Anders Behring Breivik, had gone on the rampage at a Labour Party youth summer camp after setting off a bomb in central Oslo that killed eight.

It took police around an hour to get from Oslo to Utoeya island, 40 km (25 miles) away, but the head of the commission appointed by police said no officers hesitated in their duty and criticism was unreasonable.

During a very intense action, time for planning and reflection is highly limited, the commission's head, Olav Soenderland, told a news conference.

It would be unreasonable to use the knowledge we have in hindsight as the basis for evaluating the effort on the ground.

Court-appointed psychiatrists have concluded the anti-immigration shooter, who killed 69 people on Utoeya, may be criminally insane and therefore escape jail.

Soenderland acknowledged that the first responders accidentally swamped a rubber boat heading to the island, losing precious minutes, but characterised the incident as a learning point.

What was done was consistent with the desire to get to Utoeya as quickly as possible, he said.

He said the fact that emergency phone lines were overwhelmed during the island shooting had no effect on the police response.

As well as the police report, due in March, a parliamentary committee and an independent commission appointed by the government are also evaluating the police response.

(Reporting by Oslo newsroom; Editing by Ben Harding)