Eighty-seven people turned up at Christchurch Hospital yesterday after the massacre across two mosques in the city, and three others presented at other community clinics.
Canterbury DHB chief executive David Meates this morning said 20 people were seriously injured.
"At this stage we've got 12 still in ICU - seven in our special surgical care area, one in orthopaedic trauma unit," he said.
"Then we've got a range of the remaining patients in a range of different units and wards throughout Christchurch Hospital.
"Round about 20 of them are at the more serious end."
A 28-year-old man is due to appear in Christchurch District Court this morning, facing a murder charge.
The main shooter has been identified by Australian police as Brenton Tarrant — a white, 28-year-old Australian-born man, who uploaded to his Twitter account before the shooting a manifesto explaining his intentions.
Two of the three other people apprehended yesterday remain in custody.
The fourth person was found armed at the scene but didn't appear to have had anything to do with the killings.
Police were still "working to understand" what involvement the other two, who were also armed, had in the shootings.
A large police presence remains in Christchurch, and a heightened police presence can be expected at community events nationwide for safety and reassurance.
Dozens more officers will be sent into the region today, and the Police Eagle Helicopter has been deployed to Christchurch to assist with inquiries on the ground.
Wally Haumaha, the Deputy Commissioner of Maori and Ethnic Services, has travelled to Christchurch with 15 ethnic liaison officers.
Speaking to media at Parliament last night, Ardern described the attack as "an act of terror".
She said New Zealand represents kindness, compassion and a home for those who share New Zealand's values.
"Those values, I can assure you will not and cannot be shaken by this attack."
Speaking directly to the killers, Ardern said: "You may have chosen us, but we completely reject and condemn you."