The order was announced by the president Thierry Santa and the French High Commissioner Laurent Prevost after two more infections were confirmed.
One case concerns a local pharmacist in her 60s who has not travelled recently, which means the virus is now considered to be in circulation in the community.
Since the announcement, a fifth Covid-19 has been confirmed.
The new regulations ban public and private meetings and entail the closure of non-essential businesses.
Supermarkets and pharmacies are allowed to remain open.
Full details of the new restrictions will be rolled out in the course of today.
The restrictions will be policed, with a warning that a curfew might be imposed.
Reports say residents in a town of Canala in the north of the main island blocked a bridge to stop access.
Near the airport at Tontouta, a group held a demonstration on Saturday, calling for tougher measures.
A minimal number of flights remain scheduled to allow stranded non-residents to leave and New Caledonians abroad to return.