"It is clear that this can now only be described as a terrorist attack," she said. "From what we know, it does appear to have been well planned."
"Two explosive devices attached to suspect vehicles have now been found and they have been disarmed," she added.
Meanwhile Australia's Prime Minister Scott Morrison said the gunman who killed numerous worshippers in a ew Zealand mosque on Friday was a right-wing extremist with Australian citizenship.
Morrison said the shooting in Christchurch was carried out by "an extremist, right-wing, violent terrorist" who was an Australian-born citizen.
He declined to provide further details, saying the investigation was being led by New Zealand authorities.