Horst Westenfelder, a 64-year-old German national, died on July 2 at an overseas hospital from medical complications while receiving treatment for injuries he received during the eruption, police said.

White Island, New Zealand's most active volcano, lies 48 kilometres offshore from Whakatane, on the east coast of New Zealand's North Island.

There were 47 people sightseeing on the privately owned island when the volcano erupted on December 9.

Confirmation of the Westenfelder's death was completed "as soon as practically possible," a police spokesperson said.

A coroner had to rule that the death was due to injuries suffered in the explosion and all relevant parties had to be notified first, police said.

It was "unbelievable" how many months Westenfelder had fought for his life, his wife Angelika was cited as saying in a police statement.

"It is an irreplaceable loss for our family, his friends and of course for myself. In loving memory of a full and exciting life. I will always miss you."

To mark the anniversary of the eruption, a remembrance event for families and emergency responders will be hosted by the local Maori tribe, Ngati Awa, with a minute's silence to be observed at the time of the eruption.

Ngati Awa plan to host a larger and more inclusive event when international borders re-open.

Australian Associated Press