Tongan Prime Minister 'Akilisi Pohiva, who has taken over the Pacific Islands nation, has died.

Mr Pohiva, 78, who died on Thursday at the Auckland City Hospital in New Zealand after suffering from pneumonia.

In 2010, Political Adviser Lopeti Senituli said: "He will be remembered as the champion of democracy and in the country's constitution.

Mr. Pohiva what is known for his fight against global warming.

Archipelagos like Tonga, which is made up of 171 islands and is home to 106,000 people, are vulnerable to rising seas.

He spent more than three decades in office after he was first elected to Tonga's parliament in 1987.

In 2013, the first Pacific Islander became the Defender of Democracy Award, presented by New York-based non-profit Parliamentarians for Global Action.

"His political career has been marked by battles with the Tongan monarchy over democracy, transparency and corruption," the non-profit organization wrote, noting that imprisoned in 1996 for the Supreme Court order.

"Hey what an immensely significant figure," said Graeme Smith, a research fellow at the Australian National University.

As prime minister, he was very influential in the region and a very strong voice for Tonga. Regionally, and globally, he wants to be tremendously missed. "

Mr Smith has said he has a permanent legacy of strong democracy in Tonga, because he continues to push back from vested interests, including the royal family and the nobility.

For now, politician Semisi Sika is Tonga's acting prime minister.

The Duke and Duchess of Sussex met Tongan prime minister Akilisi Pohiva
The Duke and Duchess of Sussex met Tongan prime minister Akilisi Pohiva last year (Phil Noble / PA)

Before becoming a politician, Mr. Pohiva taught history and sociology at the University of the South Pacific.

His wife Neomai Pohiva last year and the couple had seven children.

He spoke at a 2006 pro-democracy rally in the capital Nuku'alofa shortly before rioters destroyed much of the city center.

108 million dollars (£ 88 million) to China's Export Import Bank, equivalent to about 25% of GDP, a level of indebtedness that worries many observers.

Mr Pohiva was first elected prime prime minister in 2014 and won re-election three years later. His recent tenure was marked by bouts of ill health.

Fijian Prime Minister Voreqe Bainimarama wrote on Twitter that Mr. Pohiva "inspired the world with raw emotion" last month at the Pacific Islands Forum in Tuvalu.

He said Mr. Pohiva has taken charge of his poor health because he recognised the urgency of climate change, adding, "We must honor his legacy by continuing this fight."