Nuku'alofa, Tonga. New Zealand’s Māori King, Kiingi Tuheitia Pootatau Te Wherowhero VII, died Friday at age 69, days after the celebration of his 18th year on the throne.

He was the seventh monarch in the Kiingitanga movement, holding a position created in 1858 to unite New Zealand's Indigenous Māori tribes in the face of British colonization.

Tuheitia died in hospital after heart surgery, said Rahui Papa, a spokesperson for the Kiingitanga, the Māori King Movement, in a post on Instagram.

The movement's primary goals were to end the sale of land to non-Indigenous people, stop inter-tribal warfare, and provide a springboard for the preservation of Māori culture, the Waikato-Tainui tribe website said. The monarch has a largely ceremonial but still consequential role in New Zealand, where Māori make up close to 20 percent of the population.

“The death of King Tuheitia is a moment of great sadness for followers of Kiingitanga, Maaoridom and the entire nation,” Papa wrote on social media.

New Zealand Prime Minister Christopher Luxon paid tribute to Tuheitia, saying 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," Luxon said, using the country’s Māori and English names, "his commitment to mokopuna (young people), his passion for te ao Māori (the Māori world), and his vision for a future where all people are treated with dignity and respect.”

In recent months, Tuheitia has coordinated national unity talks for Māori in response to policies of Luxon's center-right government. Critics accuse the government of being anti-Māori in its efforts to reverse policies favoring Indigenous people and language.

King Charles III, New Zealand’s constitutional head of state, and his wife, Queen Camilla, were “profoundly saddened” by Tuheitia’s death.

“I had the greatest pleasure of knowing Kiingi Tuheitia for decades. He was deeply committed to forging a strong future for Māori and Aotearoa New Zealand founded upon culture, traditions and healing, which he carried out with wisdom and compassion,” Charles said in a statement.

The week before Tuheitia’s death, thousands traveled to Turangawaewae Marae, the Māori King Movement headquarters in the town of Ngāruawāhia, for annual celebrations of the king’s ascension to the throne.

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

“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,” Papa said.