The Australian Flag is being flown at half-mast around the country in a sign of condolence, and the prince will be honoured with a 41-gun salute at the federal Parliament House in Canberra at 5pm on Saturday evening.

Queen Elizabeth's husband died on Friday, two months before his 100th birthday and only a short time after a month-long stay in hospital.

Australia and the broader "Commonwealth family" would be mourning with the Queen, Mr Morrison said.

"But also, we give thanks for the life of who you described as your strength and your stay," the Prime Minister said.

"Memories of him will of course tell stories of his candour, and a unique and forceful and authentic personality.

"But above all, he was a man who was steadfast, who could be relied upon, always standing by his Queen."

Prime Minister Scott Morrison also signed a condolence book at Sydney's Admiralty House, along with Governor-General David Hurley.

Gun salutes marking the death of the Duke of Edinburgh will also take place across the UK, in Gibraltar and at sea.

Saluting batteries will fire 41 rounds at one round every minute from midday in cities including London, Edinburgh, Cardiff and Belfast, as well as Gibraltar and from Royal Navy warships, the UK's Ministry of Defence said.

The salute in Canberra will take place later in the afternoon.

Gun salutes have been fired to mark significant national events in Britain since as early as at least the 18th century. They were used to mark the deaths of Queen Victoria in 1901 and Winston Churchill in 1965.

Prince Philip visited Australia 21 times, the first in 1940 before his marriage, as a midshipman aboard the battleship Ramillies.

Some of his trips to Australia earnt international headlines for controversial comments.

On one occasion he asked an Aboriginal elder: "Do you still throw spears at each other?".

However, Mr Morrison said Australians had fond, emotional memories of the Duke too.

"There were also moments of deep compassion, in particular in the terrible bushfires of 1967 in Tasmania, where he comforted the victims and he toured the burnt-out Cascade Brewery."

Australia was thinking of the Queen and her family in their grief, he said.

"We also, your Majesty, say to you as a Commonwealth, let us also now be your strength and stay, as you continue to endure, as you continue to serve so loyally and so faithfully, as you have done over so many generations."

Former prime minister Tony Abbott, who was criticised for appointing the Duke as a Knight of the Order of Australia - an award no longer presented - said the world seemed "a little emptier" after his death.

"He combined great character with being a dutiful royal and demonstrated over eight decades there is no better life than one lived in service to others," Mr Abbott wrote.

The Australia Republic Movement offered its condolences to the royal family.

"For almost 70 years he provided unwavering support to Australia's head of state, Queen Elizabeth II, making a significant contribution to the community as consort of the British monarch," chair Peter FitzSimons said in a statement.

Former Australian prime minister and republican Malcolm Turnbull posted a brief message on Twitter.

"Farewell Prince Philip - always charming to this republican."

Chief executive of the Duke of Edinburgh's International Award Australia Peter Kaye encouraged all recipients to wear their badges on June 10 to mark the prince's 100th birthday.

"We'll still proceed with celebrations of his life and the living legacy that he's left this generation and future generations of young people," he told ABC TV.

Prince Philip had not wanted a state funeral in the UK, but will be farewelled formally in Australia.

Mr Morrison will visit the governor-general to sign a condolence book on Saturday, and on Sunday will attend Sydney's St Andrews Cathedral.

Australians can visit www.pmc.gov.au to share their condolences, which will be passed on to the Queen, he said.

The opportunity to write a 'hard copy' message with also be available, through local members of parliament.

"We are praying for Her Majesty, the Queen and her family, that they may know the comfort of Christ at this difficult time," Bishop Peter Hayward of the Anglican Diocese of Sydney said.

"A marriage of over 70 years standing and a life of service to the Commonwealth through war and peace, is a testament to Prince Philip's loving care and strong sense of duty."

Australian Associated Press