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

The death was confirmed early on Friday morning, August 30.

'Kiingi Tuheitia Pootatau Te Wherowhero VII has died peacefully ... accompanied by his wife Makau Ariki and their children Whatumoana, Korotangi and Ngawai Hono I Te Po,' the statement read.

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.

Tuheitia succeeded his mother, Te Arikinui Dame Te Atairangikaahu, following her death in 2006.

New Zealand media reported the king’s funeral was likely to take place next Thursday and that he would be buried alongside his mother, Queen Dame Te Atairangikaahu, and previous Maori kings on the sacred Taupiri Mountain.

New Zealand Prime Minister Christopher Luxon led the tributes as flags on government and public buildings were flown at half-mast.

“Today, we mourn,” Luxon said in a statement from Tonga, where he is attending the Pacific Islands Forum.

“His unwavering commitment to his people and his tireless efforts to uphold the values and traditions of the Kiingitanga have left an indelible mark on our nation.

“I will remember his dedication to Aotearoa New Zealand, his commitment to mokopuna [young people], his passion for te ao Maori [customs], and his vision for a future where all people are treated with dignity and respect.”

Britain’s King Charles III, New Zealand’s formal head of state, said he was “shocked” by the news, having recently spoken to King Tuheitia by phone.

“My wife and I were profoundly saddened to learn of the death of Kiingi Tuheitia,” the king said in a statement.

“I had the greatest pleasure of knowing Kiingi Tuheitia for decades.

“He was deeply committed to forging a strong future for Maori and Aotearoa-New Zealand founded upon culture, traditions and healing, which he carried out with wisdom and compassion,” he said, using the country’s Maori and English-language names.