Tupou VI has been formally crowned King of Tonga by an Australian citizen in front of thousands of people including heads of state and dignitaries from around the world.

Because it is taboo for Tongans to touch their king's head, a retired Australian Methodist minister was flown in to Tonga to perform the crowning which was televised.

Tupou VI, 55, ascended to the throne following the death of his bachelor brother Tupou V, who died in 2012.

An estimated 15,000 people, mainly expatriate Tongans, flew in for the coronation.

New Zealand was represented by Governor-General Sir Jerry Mateparae.