SYDNEY (Reuters) - Australia and New Zealand on Sunday celebrated the coronation of King Charles III with 21-gun salutes in their capitals, after the countries' leaders, both republicans, attended the coronation ceremony in London.

King Charles is head of state in Australia, New Zealand and 12 other Commonwealth realms outside the United Kingdom, although the role is largely ceremonial.

Both nations held events on Sunday to celebrate the coronation, with ABC television broadcasting a 21-gun salute in front of Australia's parliament in Canberra.

A military flypast scheduled to take past afterwards was cancelled due to poor weather, Defence Australia tweeted.

In New Zealand, the NZ Defence Force said the army fired a 21-gun salute from Point Jerningham in the capital Wellington.

Australian Prime Minister Anthony Albanese and his New Zealand counterpart Chris Hipkins were in London on Saturday for the coronation at Westminster Abbey.

Both Albanese and Hipkins are in favour of their countries breaking with the monarchy, but said they would still pledge their allegiance to King Charles.

The death of Queen Elizabeth last September reignited debate, particularly in Australia, about the need to retain a distant constitutional monarchy.

The country held a referendum in 1999 on becoming a republic with 55% of voters opposed, while more recent polls have shown varying levels of support.

(Reporting by Sam McKeith; Editing by Kim Coghill)