Nine people remain in hospital in a critical condition. Many public vigils have been held across New Zealand over the weekend for the victims of the attacks, and more are planned for this week.
On Monday afternoon, about 3,000 high school and college students held a vigil in Hagley Park near the Al Noor mosque, one of the two mosques attacked on Friday.
At the weekend, Ms Ardern said the suspect had a gun licence, obtained in November 2017, and owned five guns.
Earlier on Monday, gun retailer Gun City said it had sold weapons to the man charged with murder, but not the high-powered weapon used in the mosque shootings.
New Zealand's Police Association has called for semi-automatic weapons to be banned,