Queen Elizabeth II has died, aged 96, at Balmoral.

A statement from Buckingham Palace on Thursday (Friday morning AEST) confirmed her 70-year reign had come to an end.

"The Queen died peacefully at Balmoral this afternoon," Buckingham Palace said.

"The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."

As news of the monarch's death ricocheted around the world, thousands of people gathered outside Buckingham Palace on a rainy London night to pay their respects.

There were similar scenes outside the Queen's Windsor Castle home and Balmoral, in Scotland, where she spent her final days.

Portraits of Elizabeth were posted on billboard screens in central London's Piccadilly Circus and the city's Canary Wharf financial district.

Echoes of 'God Save The Queen' rung out.

His Majesty the King, Charles III, paid tribute to his "beloved mother".

"We mourn profoundly the passing of a cherished sovereign and a much-loved mother," he said. "I know her loss will be deeply felt throughout the country, the realms and the Commonwealth, and by countless people around the world."

The new King said his family's mourning would be comforted "by our knowledge of the respect and deep affection in which The Queen was so widely held."

Prince Harry and Meghan Markle's website for their nonprofit organisation Archewell has transformed with a simple tribute.

The website is completely black, with a message stating: "In loving memory of her majesty Queen Elizabeth II 1926-2022".

Newly appointed British Prime Minister Liz Truss met with the Queen on September 6 as is customary to form a new government. It was the monarch's final engagement.

Truss said Queen Elizabeth had been with her nation "through thick and thin".

"She was the very spirit of Great Britain and that spirit will endure," Truss said from outside 10 Downing St, in an emotional television address.

"Our country has grown and flourished under her reign. Britain is the great country it is today because of her."

"Queen Elizabeth II was the rock on which modern Britain was built" Prime Minister Liz Truss pays tribute to the Queen Elizabeth II, who has died aged 96 https://t.co/qmv4KQNpMs pic.twitter.com/TVoyQ4Grb0

— BBC News (UK) (@BBCNews)

She encouraged Britons to come together in support of their new King, Charles III.

"With the King's family, we mourn the loss of his mother. And as we mourn, we must come together as a people to support him. To help him bear the awesome responsibility that he now carries for us all."

She concluded: "With the passing of the second Elizabethan age, we usher in a new era in the magnificent history of our great country, exactly as Her Majesty would have wished, by saying the words... 'God save the King.'"

In Australia, Prime Minister Anthony Albanese led the country's mourning.

"Her majesty celebrated our good times, and she stood with us during trials and hardships, happy and glorious," Albanese said in a televised address on Friday morning.

#Breaking: "May she rest in eternal peace." Australian Prime Minister Anthony Albanese has addressed the nation for the first time since the Queen's death, expressing Australians' "profound sadness and grief" over the loss of Britain's longest-serving monarch. pic.twitter.com/bSr3cMY3Y4

— 10 News First (@10NewsFirst)

In the coming days the prime minister will travel to London with Governor-General David Hurley to convey the sorrow of Australians.

Queen Elizabeth visited Australia 16 times during her reign, visiting every state and territory.

"Throughout her reign Queen Elizabeth II showed her deep affection for our country," Albanese said.

"As she said at the Sydney Opera House in the year 2000, 'Since I stepped ashore here, I have felt part of this rugged, honest, creative land and I have shared in the joys and sorrows, the challenges and the changes that have shaped this country's history.'

"Her Majesty celebrated our good times, and she stood with us during trials and hardships, happy and glorious but steadfast too.

"In particular, we recall the sympathy and personal kindness she extended to Australians afflicted by tragedy and disaster from floods and bushfires."

Listen to Mamamia's daily news podcast, The Quicky. Post continues below.

Queen Elizabeth II was the only reigning monarch many had known and the only one to visit Australia, the prime minister said.

"Today marks the end of an era, the close of the second Elizabeth's age.

"This time of mourning will pass but the deep respect and warmth regarding which Australians have always held for Her Majesty will never fade."

Opposition leader Peter Dutton said in a statement there had never been "a more dignified monarch, a more dutiful leader, or a more decent human than Her Majesty Queen Elizabeth II".

"An extraordinary life which touched so many has sadly come to an end," he continued.

"The last page has been inked on an exceptional reign."

Governor-General David Hurley said Australians should take inspiration from the Queen's contribution.

"When I reflect on my own memories – she was my Queen for my whole life – I think of Her Majesty's dignity and her compassion. Her dedication and tireless work ethic. And her selflessness and unwavering commitment to the people that she served. To us," he said in a statement.

Across the world, leaders and citizen have paid their own respects to the woman who had been the face of her nation for more than 70 years.

Other Commonwealth leaders, including New Zealand Prime Minister Jacinda Ardern and Canadian Prime Minister Justin Trudeau, shared emotive statements honouring the monarch.

"Over her reign she has come to define notions of service, charity and consistency. Her commitment to her role and to all of us has been without question and has been unwavering," Ardern said.

"She has also demonstrated courage and compassion and humour. A strong memory I will have of her is her laughter. She was extraordinary."