New Zealand's Prime Minister Jacinda Ardern has gone into self-isolation until Tuesday after being deemed a close contact of a person who tested positive for Covid-19, the government said.

The exposure took place on Jan 22 during a flight to Auckland from the town of Kerikeri, the government said in a statement on Saturday, adding that the result of whole genome sequencing was expected the following day.

That would show if the infection was caused by the Omicron variant of coronavirus, it said.

Ardern, who is asymptomatic, is feeling well, the statement added. She will be tested on Sunday and is in isolation in line with the health ministry's directives.

The governor-general and members of her staff, who were also on board the flight, are following the same isolation procedure.