Police said schools in the area are in lockdown as they search for attacker, who fled after the incident.
New Zealand has no active Covid-19 cases after the country's final patient was given the all clear and released from isolation.
About 47 productions were underway when Prime Minister Jacinda Ardern imposed a tough lockdown on March 26 to stop the spread of the coronavirus.
To get back on their feet, many countries have started the process of easing the coronavirus lockdown, introducing the staged relaxation of quarantine rules.
After nearly five weeks at the maximum Level Four restrictions, with only essential services operating, the country will move to Level Three late on Monday.
The COVIDSafe app uses a phone's Bluetooth wireless signal to store information about people's interactions, and can be accessed by health officials if a person contracts coronavirus.
Larger shops and those in major German cities will open later as part of an attempted phased return to a more normal existence that will also see some students go back to school from May 4.
Leaders around the world are wrestling with the dilemma of how to return to normal and kickstart their shattered economies without risking a devastating second wave of infections.
The attacks on mosques in New Zealand made it impossible to deny the threat from right-wing terrorism.
The event, to be held in Christchurch on Sunday, was expected to attract a large crowd, with many travelling from around New Zealand and from overseas.
Prime Minister Jacinda Ardern was in Christchurch attending events to mark the anniversary of last year's March 15 massacre, which she has described as one of New Zealand's darkest days.
The centre-left leader announced Kiwis would go to the polls on September 19, two months ahead of the last possible date for the ballot, when she will seek a second three-year term.
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