Christchurch, Mar 29 (AFP) A Maori lament echoed across Christchurch Friday as a survivor of the New Zealand mosque attacks told a national remembrance service he had forgiven the gunman responsible for the racist massacre that shocked the world.

Thousands attended the service in the grieving southern city, standing silently with heads bowed while the names of 50 people killed by a self-avowed white supremacist gunman were read out.

Speakers honoured the dead and those who survived the March 15 attacks, including 22 people who remain in hospital, among them a critically injured four-year-old girl.

Wearing a traditional Maori cloak, Prime Minister Jacinda Ardern was joined by representatives from nearly 60 nations, including her Australian counterpart Scott Morrison.

Ardern, who has been widely hailed for her response to the tragedy and received a prolonged standing ovation when she took the stage, praised the way New Zealanders had embraced their devastated Muslim community since the attacks.

"Racism exists, but it is not welcome here," she said.

"An assault on the freedom of any one of us who practice their faith or religion is not welcome here. Violence and extremism in all its forms is not welcome here."

The hastily organised service was held amid tight security, with Police Commissioner Mike Bush confirming armed police from Australia were on site to assist their New Zealand counterparts.

The service heard a Muslim invocation, or du'a, and Cat Stevens -- the British singer who shunned stardom in the 1970s and became a Muslim, taking the name Yusuf Islam -- gave a powerful rendition of his hit song "Peace Train".

But the most moving speech came from Farid Ahmed, whose wife Husna was killed as she rushed back into a mosque trying to rescue her disabled husband.

Sitting in his wheelchair before the assembled crowd, Ahmed said he forgave the accused gunman, Australian Brenton Tarrant.

"People ask me, 'why do you forgive someone who has killed your beloved wife?'" he said.

"I can give so many answers... Allah says if we forgive one another he loves us." Echoing Ardern's theme that extremism should not be allowed to breed extremism, Ahmed received a standing ovation when he said he chose peace over anger.

"I don't want a heavy heart boiling like a volcano with anger, fury and rage -- it burns itself and burns its surroundings," he said.

"I want a heart full of love, care and mercy. This heart does not want any more lives to be lost, any other human to go through the pain I've gone through.

"That's why I am choosing peace and I have forgiven." Christchurch mayor Lianne Dalziel said the atrocity was "an attack on us all".

"Those actions were designed to divide us and tear us apart," she said.

"They have instead united us." Among the crowd, Azra Chida travelled from Auckland to attend the service, saying she lost two close friends in the attack.

"I have come to see their families and pay respect and visit the patients in the hospital," she told AFP shortly before the ceremony began. Local man Bobby Turner said: "I'm here for solidarity. To show that we care.

"It was just such a horrible thing to happen. These people were just going about their business. Prayer is supposed to be about love and peace." (AFP)

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