Travel into New Zealand from India - including for New Zealand citizens and residents - is being temporarily suspended because of high numbers of Covid-19 cases, Prime Minister Jacinda Ardern says.

Director-General of Health Ashley Bloomfield confirmed this afternoon that a border worker had tested positive for Covid-19.

Bloomfield also announced 23 new positive Covid cases in managed isolation, 17 of whom had arrived from India.

Ardern says she is focusing on the new cases at the border today.

"Cases of the virus have been on the rise internationally ... with surges particularly in Brazil and India... we are starting to see this global trend mirrored here," she says.

"We are temporarily suspending entry into New Zealand for travellers from India."

The travel ban will be from 11 April to 28 April, she says, and is expected to be temporary.

It is the first time New Zealand has stopped citizens or residents from returning.

"I absolutely understand the difficulty this temporary suspension will cause," Ardern says. "I understand that, but I also feel a sense of responsibility and obligation to find ways to reduce risk that travellers are experiencing."

It is largely because of increasing numbers of cases arriving from India, with many believed to have contracted the virus while travelling to their international flight while in India.

India has been struggling with a sustained outbreak and is reporting a seven-day average of 93,000 new cases per day. The US is in second place with 64,000 and Brazil with 63,000. Turkey has 43,000 and France 36,000.

Cases in New Zealand's managed isolation and quarantine (MIQ) facilities have increased from two or three a day to four to five a day for the rolling seven-day average.

"We want to see fewer cases arriving in general," Ardern says. "Advice is people are likely getting the virus ... as they travel to an airport and before they board a plane."

She said it was "not our intention that this be a long-term tool" but she could not rule out the travel suspension being extended.

The government is not looking at suspensions for other countries at the moment, Ardern says, in part because other countries with Covid-19 surging do not have as many people travelling to New Zealand as India.

Ardern says the government has been concerned about high-risk countries for some time.

"We have looked into whether we have issues with the accuracy of pre-departure tests - that has not demonstrated that is where the problem lies, so this suspension gives us a bit of time to look at the issue more generally."

There are also significant numbers of deaths worldwide, with Brazil just yesterday reporting more than 4000 deaths in a day.

The suspension is temporary because "we do have obligations to allow citizens to return to New Zealand", Ardern says.

It would reduce the risk to New Zealand and to the travellers, she says.

Regarding the case of the security guard announced today, Ardern said her understanding was that efforts had been made to vaccinate the person in question.

"My expectation is that all front line border workers are vaccinated for their own health and safety ... from Monday, we start the process of those [workers] who have not [been vaccinated] moving to other roles."

It was announced this week that a quarantine-free travel bubble with Australia would operate from 19 April.