Mr Mahmoud said he "had to" travel to New Zealand to "stand shoulder-to-shoulder, to unite as Muslims, to unite as human beings, against this terror and such aggression".
Mr Bridges said the Royal Commission would need to ask hard questions about whether security and intelligence agencies had their focus in the right places.
Ardern ruled out New Zealand re-introducing the death penalty for accused gunman Brenton Tarrant, 28, who was arrested minutes after the attack on the mosques and has been charged with murder.
Saudi King Salman said, "The heinous massacre of the safe worshipers of mosques in New Zealand is a terrorist act and underlines the responsibility of the worldwide community to confront the rhetoric of hatred and terrorism, which is not recognised by religions or values of coexistence among peoples".
Prime Minister Jacinda Ardern said the country's highest form of investigation, a royal commission of inquiry, was appropriate for "matters of the gravest public importance".
Mourners listened while the names of 50 worshippers were read aloud, beginning with the youngest victim, 3-year-old Mucaad Ibrahim, reports Al Jazeera.More news: Emilia Clarke Reveals She Survived 2 Life-Threatening Brain Aneurysms
More news: Gophers defeat Louisville 86-76 to advance in NCAA Tournament
More news: Facebook blames AI for failing to catch New Zealand attack video
People attend the Friday prayers at Hagley Park outside Al-Noor mosque in Christchurch, New Zealand March 22, 2019.
"The service will be a chance to once again show that New Zealanders are compassionate, inclusive and diverse, and that we will protect those values", she said.
Ardern has been widely praised for her response to the attack, meeting victims' families and quickly acting to tighten gun laws in the country.
The act of remembrance was organised to mark one week since a suspected far-right terrorist killed 50 people in shootings at two mosques, streamed live on Facebook. On Friday, people across the nation observed the Muslim call to prayer one week after the attacks.
Most of the dead were laid to rest at a mass burial in Christchurch on Friday when 26 victims were interred.
Shahadat Hossain, whose brother Mojammel Haque was killed in the attack, arrived in New Zealand on Saturday to bring his brother's body back to Bangladesh.