Jacinda added that the terrorist was brought down within 36 minutes of the attack.
Eleven people remained in intensive care, hospital authorities said.
The 28-year-old Australian Brenton Tarrant who has been charged with murder in connection with the attack appeared to be the sole gunman, Bush said.
Police and military personnel walk at the carpark compound of the district court after Friday's mosque attacks, in Christchurch, New Zealand, March 16, 2019.
The death toll rose to 50 victims after investigators found another body in the mosque, said New Zealand Police Commissioner Mike Bush. "Just helping people is his main thing".
"We appear to primarily be dealing with one primary perpetrator, but we want to make sure that we don't take anything for granted in ensuring New Zealanders' safety", Prime Minister Ardern said. Police believe that Tarrant single-handedly carried out the terror attack at both the mosques during the ongoing Friday prayers for which a large number of people had congregated.
The New Zealand Red Cross has published a list of missing persons on its website.
"I think the public should be assured that we train for this, hoping we never, ever have to respond", he said.
For nearly 3 days forensics teams have been working through multiple crime scenes - at the Al Noor and Linwood mosques as well as a house in Dunedin, the southeastern city where the Tarrant lived.
"I was very happy to hear the prime minister's comments this morning that there will be a change in the gun law, but I can't say any more than that", he told reporters on Saturday.
The majority of victims were migrants or refugees from countries such as Pakistan, India, Malaysia, Indonesia, Turkey, Somalia and Afghanistan. He said he survived by played dead, but was desperate to know what happened to his friends who were there with him. She said her office sent it to parliamentary security two minutes after getting it.
Facebook said it had removed 1.5 million videos of the attack from the social media platform within 24 hours of the incident.
Ardern said the main suspect was a licensed gun owner who used five weapons during his rampage, including two semi-automatic weapons and two shotguns.
But despite the horror of the Christchurch shootings, some local residents who AFP spoke with Saturday warned against any drastic moves on gun control.
New Zealand tightened its gun laws to restrict access to semi-automatic rifles in 1992, two years after a mentally ill man shot dead 13 people in the southern town of Aramoana.