Wellington: Tongan Prime Minister 'Akilisi Pohiva, a pro-democracy and climate change campaigner in the South Pacific, has died in a New Zealand hospital, the Information Ministry said.

Pohiva, 78, had been diagnosed earlier this year with a liver complication and was admitted to a hospital in Tonga two weeks ago for pneumonia, the Prime Minister's office said in a statement on Wednesday. Medical experts decided he should be medically evacuated to New Zealand.

Parliament has been deferred indefinitely, Tongan media said.

Known as a champion for democracy, Pohiva's political career was marked with constant battles against the monarchy of the South Pacific nation. He was charged with sedition in wake of pro-democracy riots in the capital Nuku'alofa in 2006.