Christchurch Muslims are praying at home on the first anniversary of the mosque shootings after the official national memorial service was cancelled over coronavirus fears.

The national remembrance service to honour the 51 people killed on March 15 last year at the two main Christchurch mosques was expected to attract a large crowd at Horncastle Arena this afternoon, with many travelling from around New Zealand and overseas.

But Prime Minister Jacinda Ardern says she took the "pragmatic" and precautionary approach to call it off yesterday afternoon.

"We're very saddened to cancel, but in remembering such a terrible tragedy, we shouldn't create the risk of further harm being done," Ardern said.

An official unveiling of a remembrance plaque at Masjid An-Nur planned for this morning was also ditched because of the increasing Covid-19 concerns.

There was a heavy police presence at the mosque where 42 worshippers were gunned down a year ago.

Deans Ave is cordoned off to all traffic except residents.

But there's a relaxed, quiet atmosphere at the mosque where a new, colourful mural featuring the prime minister in a hijab, along with a police officer in a headscarf, has been placed at the front wall, along with signs in English and Arabic that say, "Spread peace", "Feed others", and "Strengthen ties".

Rahimi Ahmad, who was shot in the hip at Al Noor and is still recovering, had planned to attend the remembrance event today but instead is at home with his family.

"For us, the Government has done their best and right decision to cancel this event. For us, we support their decision without any doubt or disappointment," said Ahmad.

The imams of the two mosques targeted last year have come together today to issue a joint message, called "The Christchurch Invitation".

Linwood Islamic Centre Imam Alabi Lateef Zikrullah says that the global response to the terror attacks has been humbling.

"We have been inundated with gestures of love and compassion, with gifts and heartfelt words. Despite the magnitude of the tragedy, many of us have never felt prouder to call New Zealand home and ourselves New Zealanders," he said.

"The response has shown us that for every person who wants to spread hate and divide us, there are many thousands more who want to spread peace and belonging.

"One year on, we are inviting all communities to come together, celebrate our diversity, and build a better future for everybody."

Imam Gamal Fouda from Masjid An-Nur says The Christchurch Invitation is informed by three calls to peace the Prophet Muhammad promoted when he migrated from Mecca to Madinah to help people in dispute.

"The Prophet Muhammad (peace be upon him) identified three simple actions everyone can do to create a kinder and more compassionate community – spread peace, reconnect with others and the world around us, and feed the hungry," Fouda said.

"Thousands of people from all over the world have asked us how they can help us, and what can they do. Overcoming division, and creating a kinder and more peaceful world, starts with these three simple actions.

"Doing more of these actions, more often, will help us truly become one."

The streets, bars, cafes, and parks of central Christchurch are quieter than a usual Sunday.

There are still some joggers and cyclists enjoying the open spaces of Hagley Park, and supermarkets are busy, but the city has a subdued feel – with many spoken to by the Herald feeling it was a result of the rising coronavirus bad news, with an Akaroa cruise ship passenger quarantined and tested with suspected Covid-19, coupled with the March 15 anniversary.

At a press conference in the city on Friday, Prime Minister Ardern acknowledged that Christchurch has "experienced more than any region should have to endure".

One city motel cleaner spoken to by the Herald today spoke how she was trying not to think about it.

"I'm constantly on edge here, between the mosques and quakes."

If it wasn't for her mum and daughter here, she would have left.

"How much can one city go through?" she asked, pausing mid-conversation when a police car sped past with its siren blaring.

"I hate that noise," she says. "Whenever I hear it, it reminds me of last year. We knew something was going on because there were so many of them. The guests left the motel and just watched all the police and mufti police fly down Bealey Ave.

"Every time I hear one, I'm afraid there will be more."

- Additional reporting, Will Trafford.