New Zealand's Maori King Tuheitia dies at 69 after heart surgery

New Zealand's Maori King, Kiingi Tuheitia, has died age 69, just days after the celebration of his 18th year on the throne.

The death was confirmed by the Kiingitanga's social media early on Friday morning.

"Kiingi Tuheitia Pootatau Te Wherowhero VII has died peacefully this afternoon, accompanied by his wife Makau Ariki and their children Whatumoana, Korotangi and Ngawai Hono I Te Po," it read, in te reo, the Maori language.

King Tuheitia was in hospital recovering from heart surgery.

"It didn't quite go as we had all hoped," the Kiingitanga's chief of staff Ngira Simmonds told Radio NZ.

"In the early hours of this morning he passed away peacefully."

The king died days after celebrating the 18th anniversary of his coronation. (AFP: Peter Drury: POOL)

The Maori king position was founded in 1858, aiming to be a unifying movement for all Maori tribes.

It is a largely ceremonial but hugely consequential role in New Zealand.

In recent months, King Tuheitia has co-ordinated national unity talks for Maori in response to the centre-right government's policies.

"He believed in the vision of his ancestors. He understood his role and his duties," Mr Simmonds said.

"He wanted to serve and do everything that he could and exhaust every effort to bring unity to our people and indeed the nation at large.

"He served until the very last."

Leaders across New Zealand and the Pacific have paid tribute to Kiingi Tuheitia.

Former prime minister Dame Jacinda Ardern has led tributes to the king, describing him as "an advocate for Maori, for fairness, justice and prosperity".

"You worked tirelessly on building understanding and knowledge of our shared history and in doing so, strengthening Aotearoa."

"I'm sure that the people of Tonga feel the loss of this great leader of the Pacific," said Hu'akavameiliku Sioasi Sovaleni, Tonga's prime minister.

"Our thoughts and prayers are with New Zealand."

He said the relationship between Aotearoa New Zealand and Tonga was strengthened by the ties between the two royal families.

Last week, thousands travelled to Turangawaewae Marae for annual celebrations of the king's ascension to the throne, including politicians.

The seat of the Maori king is held by the Tainui tribes in the Waikato and it is not yet clear who will take the throne.

"The death of Kiingi Tuheitia is a moment of great sadness for followers of Te Kiingitanga, Maaoridom and the entire nation," Rahui Papa, a Kiingitanga spokesman, told TVNZ.

"It is expected that Kiingi Tuheitia will lie in state at Turangawaewae Marae for five days before he is taken to his final resting place on Taupiri Mountain."

Mr Simmonds said the next few days would be for local tribes to mourn.

Others would then be welcomed to the marae, including international dignitaries, followed by a Maori funeral, known as a tangihanga.

AAP