New Zealanders are dying from Covid-19 at record rates as the country battles a new wave of the Omicron strain that is particularly affecting the older population.

Deaths from the virus reached 151 in the seven days to July 16, compared with 115 in the worst week of the previous wave, in March, according to Health Ministry data. In the latest 24 hours, 26 people died from Covid, all aged over 60, the ministry said in a statement on Friday.

The Omicron BA.5 sub-variant is driving the current wave in New Zealand, which has 5.1 million people. There have been 64,780 active cases in the past seven days, although authorities say many infections are unreported.

Once regarded as a model for preventing Covid infection, New Zealand's swift response to the pandemic and its geographic isolation kept it largely free from the virus until the end of last year.

The government dropped its zero-Covid policy this year once the population was largely vaccinated. Since then, the virus has been allowed to spread.

Emergency departments, general practices and medical centres are under pressure. However, Health Ministry data shows hospitalisation levels remain below those seen during the March peak.

The government is resisting pressure from some doctors to reinstate curbs on public gatherings or mandate the wearing of masks at schools.

However, Education Ministry chief Iona Holsted said on Thursday the ministry had advised schools to enforce the wearing of masks as much as practicable when children return from holidays next week.

"We understand that implementing mask policies can be a challenge but ask that you take action to strengthen your mask wearing policy as soon as possible," she said.

- Reuters