Crime scene investigations at the Masjid al Noor and Linwood Masjid have been completed and restoration work has begun.

"We, as investigators, are working very hard with a number of people to release those mosques as early as today," Police Commissioner Mike Bush said on Thursday afternoon.

"Not only have we completed crime scene investigations, we are working to restore them in a way that is absolutely respectful to those people."

Local contractors in Christchurch have donated their services to help get both mosques back to their original condition ahead of Friday prayers, when many are expected to return.

Work has also begun to move thousands of floral tributes laid outside the police cordon closer to the mosque.

"The Muslim community has requested that we bring the flowers to near the front of the mosque to allow them to be seen by all that come to the mosque," Christchurch Botanic Gardens director Wolfgang Bopp said.

As a national two minutes of silence is held on Friday to mark one week since the tragedy, a number of Kiwis have revealed they'll be outside the mosques to show support.

Among them are members of the Mongrel Mob and Black Power motorcycle gangs, whose offers of protection outside mosques in other New Zealand cities were met with invitations to instead join in.

Mr Bush said the police presence would continue in Christchurch and elsewhere, with daily risk assessments.

"The country itself is still in a state of high level threat," he said.

Australian Associated Press