Briefing the media immediately after the customary update on the total number of confirmed and probable cases of Covid-19 by the Director-General of Public Health Ashley Bloomfield, the Civil Defence Emergency Management director general Sarah Stuart-Black said a state of national emergency was declared at 12.21 pm and applied to all of New Zealand - including the Chatham Islands, Stewart Island and other inhabited islands.
A nationwide mobile alert will be issued to all New Zealanders between 6-7 pm tonight.
The State of Emergency legislation allows it to be in place for seven days and can be extended, said Stuart Black.
In a state of emergency, authorities will have powers that are not normally available to them, such as the possibility of military patrols.
She said there would be no tolerance for people who do not self-isolate.
Dr. Bloomfield said police would announce either later today or tomorrow what the consequences for people flouting the self-isolation rules would be.
Prime Minister speaks in parliament
Later on, speaking in parliament Prime Minister Jacinda Ardern reiterated the message of zero tolerance for those who flouted the nationwide lockdown.
"A State of National Emergency [is needed] to preserve our way of life.
"Every person still at work, interacting with others, increases the risk of the virus spreading exponentially and means we will be in lockdown for longer.
"That means people will be out of work longer, doing further damage to livelihood and lives.
"There will be no tolerance for that. We will not hesitate to use our enforcement powers if needed," the Prime Minister said.
Parliament meets to pass Epidemic Notice
Meanwhile, a small number of MPs had returned to Parliament today to debate and pass much-needed legislation as the country prepares for a nationwide lockdown tonight.
Prime Minister Jacinda Ardern issued an epidemic notice under section 5 of the Epidemic Preparedness Act 2006 on Monday when she announced the country was moving to alert level 3 immediately and alert level 4 at 11.59 pm tonight.
The epidemic notice begins tonight and will last for three months unless the government chooses to lift it earlier.
Cross-party MPs are speaking to the epidemic notice in Parliament now.