Prime Minister Jacinda Ardern is due to give an update on Tonga's volcano eruption and tsunami.

She will be joined by Defence Minister Peeni Henare and Pacific Peoples Minister Aupito William Sio.

Ardern said earlier on Sunday that officials were working to establish what support New Zealand would provide to Tonga after the devastating tsunami triggered by underwater volcano Hunga Tonga-Hunga Ha'apai erupting.

"The images of the volcanic eruption in close proximity to Tonga are hugely concerning," a statement from Ardern said.

"Communication as a result of the eruption has been difficult, but our Defence Force team and Ministry of Foreign Affairs are working as we speak to establish what's needed and how we can help.

"I know we are thinking of our Pacific friends and family."

The underwater volcano off Tonga erupted on Saturday, triggering tsunami warnings in New Zealand and causing large waves in several South Pacific islands, where footage on social media showed waves crashing into coastal homes. The volcano, which lies about 65km north of Nuku'alofa, caused a 1.2-metre tsunami wave.

Tsunami waves of 83cm were recorded by gauges in the Tongan capital of Nuku'alofa and two-foot waves were seen at Pago Pago, the capital of American Samoa, the Pacific Tsunami Warning Centre said. There have been no immediate reports of casualties.