The city still feels the wound' - Former Christchurch Mayor Sir Bob Parker

As Christchurch prepares to mark one year since the tragic mosque shootings, former Mayor Sir Bob Parker says "the city still feels the wound".

A memorial will be held on Sunday to commemorate the tragedy, which claimed the lives of 51 people. 

Sir Bob said March 15 will forever be marked by "unbelievable shock" for many people in Christchurch. 

"[The day] has a lot of emotional loading for them," he told The AM Show on Friday.

The man alleged to have carried out the shootings will face trial in June. He faces 51 charges of murder, 40 of attempted murder and one charge under the Terrorism Suppression Act.

Sir Bob said in the year since the horrific event, the Muslim community in Christchurch have been an example to follow for the rest of the city.

"I think everybody in the city observed a group of people who had such strength and courage and such a sense of forgiveness that it was utterly eye-opening and utterly stunning," he said.

"This community had strength of its own and internal strength - it was, I guess, a great advertorial for this faith."

Thousands are expected to attend the memorial on Sunday, with Christchurch Mayor Lianne Dalziel, local Muslim leaders and other dignitaries among those who will be present.

The service will be jointly held by the Government, Christchurch City Council, local iwi Ngāi Tūāhuriri and the local Muslim community.

Sir Bob said the local Muslim community has not just gained the respect of people in Christchurch, but also become a part of the city' identity.

"A group of people who were very low-key in terms of the way the city felt their presence are now very central to the way the city feels to its presence  - that's been a significant change. [There's been] a lot of learning and I think a lot of friendships have grown out of that. That's got to be a good thing that comes out of the worst thing that happened here."

Earlier this month, police increased security around the two mosques - Al Noor and Linwood -  targeted in last year's attack after a threat was made online against worshippers.

Sir Bob said he was speechless that such threats could be made.

"I think we have to look at it as a kind of an illness in people and that it's something that does need to be resolved for them and for our sake," he said.

"It's a fool's idea, a crazy, misarranged mind that would even attempt to do anything terrible here - what can you say?" 

Sunday's event was originally scheduled to be held in Hagley Park but has since been moved indoors due to wet weather forecast. 

Prime Minister Jacinda Ardern said despite fears relating to the spread of coronavirus commemorations would still go ahead, though anyone feeling unwell was urged to stay home.