New Zealand Prime Minister Jacinda Ardern described the incident as an "unprecedented act of violence".
"I would describe it as an unprecedented act of violence. An act that has absolutely no place in New Zealand. This is not who we are," she said in a press conference.
"It I can tell you now this is and will be one of New Zealand's darkest days."
Ardern confirmed that one person had been taken under custody.
"Migrants and refugees have chosen to make New Zealand their home and it is their home. For the person who perpetuated this violence it is not."