(AFP) - Thousands of mourners lined the route to pay their respects as Queen Elizabeth II's coffin on Sunday headed from the Scottish retreat where she died to Edinburgh on the first leg of her sombre final journey.

A hush fell over the gathered crowd as the cortege carrying the queen's casket exited the gates of Balmoral Castle at the start of an odyssey of mourning in the United Kingdom that will culminate in her state funeral in London on September 19.

Some well-wishers threw flowers or applauded, while others were in tears as the long convoy led by a black hearse wound its way slowly on a six-hour journey to Scotland's capital, where it will stay for two days.

Six groundskeepers had loaded the oak coffin -- draped with a Scottish Royal Standard and a floral wreath -- into the hearse that was followed by a Bentley carrying the queen's only daughter Princess Anne.

The first glimpse of the queen's coffin for a grieving nation came a day after her son Charles III was formally proclaimed king, and after her warring grandsons William and Harry, and their wives Kate and Meghan, briefly reunited for a walkabout.

The king himself will travel to Edinburgh on Monday for a prayer service, before the body of the queen, who died at Balmoral on Thursday aged 96, is flown to London on Tuesday.

Britain's longest-serving monarch will then lie in state for four days which is expected to draw at least a million people, ahead of a funeral set to be watched worldwide and attended by numerous heads of state.

"We want to say thank you that we can honour the memory of the Queen," said Ukrainian Viktoriia Saienko, who fled Kharkiv, one of the cities devastated by Russia's invasion, and is working in Scotland.

"We wanted to say thank you very much to Britain, to the Queen and all her family," the 29-year-old said as she waited in Edinburgh with a group of her compatriots clutching bouquets of roses.

- 'Poignant moment' -

The symbolism of the queen's last journey will be heavy for Scotland -- a nation with deep royal links, but where there is also a strong independence movement intent on severing the centuries-old union with the United Kingdom.

"A sad and poignant moment as Her Majesty, The Queen leaves her beloved Balmoral for the final time," Scotland's First Minister Nicola Sturgeon wrote on Twitter.

"Today, as she makes her journey to Edinburgh, Scotland will pay tribute to an extraordinary woman."

The queen's coffin will be taken to the Holyroodhouse Palace, the monarch's official residence in Scotland, where it will rest for a day.

King Charles -- who was formally proclaimed monarch in Scotland at a pomp-filled ceremony on Sunday -- and other royals will on Monday take part in a procession to convey her coffin along Edinburgh's Royal Mile to St Giles' Cathedral.

The following day the coffin will be flown by Royal Air Force jet to Northolt airfield near London, and driven to Buckingham Palace. Then, on Wednesday, it will be moved to Westminster Hall to lie in state.

King Charles will also visit Northern Ireland and Wales in a show of national unity. The new monarch will be joined at memorial services by British Prime Minister Liz Truss, who was only appointed by the late queen on Tuesday.

Charles has seen his popularity recover since the death of his former wife Diana, Princess of Wales, in a 1997 car crash, but he takes the throne at a moment of deep anxiety in Britain over the spiralling cost of living and international instability caused by the war in Ukraine.

- William and Harry together -

While Charles' accession has pushed Britain into what newspapers have called the new "Carolean" era, Britain and the royal family are still coming to terms with the end of the Elizabethan age.

Prince William broke his silence with an emotional tribute to his beloved "Grannie" on Saturday.

"She was by my side at my happiest moments. And she was by my side during the saddest days of my life," said William, who has now become the Prince of Wales.

But the queen's death also brought a surprise show of unity from William, 40, and his younger brother Harry, 37, when they emerged with their wives to speak to well-wishers outside Windsor Castle, near London.

The sight of the two couples, who have barely seen each other since 2020, together -- even if they separated to speak and shake hands with different sides of the cheering crowds -- will likely spark rumours of a reconciliation.

Pictures of the four were splashed on the fronts of Sunday's newspapers.

"Reunited for granny," read the Sunday Mirror's headline, while the Telegraph ran with "Reunited in sorrow" and the Sun with "All 4 One".

The Sunday Times focussed on the apparent frostiness, with the headline: "Warring Windsors' awkward truce to honour the Queen".

- 'Inspiring example' -

Charles vowed at the formal Accession Council at St James's Palace on Saturday that he would "strive to follow the inspiring example I have been set" by his mother during her "lifetime of service".

The centuries-old tradition was televised live for the first time, featuring a fanfare of trumpets and a court official wearing a feathered hat to declare him king from a palace balcony.

Thousands of people have gathered outside Buckingham Palace and other royal residences in recent days to lay flowers and messages of condolence, or simply to experience history in the making.

But officials expect far more people to pay their respects while the queen lies in state, before the televised funeral service at Westminster Abbey opposite.

The funeral for the queen -- who came to the throne aged just 25 in 1952 -- will be attended by national leaders including US President Joe Biden, Australian Prime Minister Anthony Albanese and possibly Japanese Emperor Naruhito.

Charles was formally named king in Australia and New Zealand -- former British colonies that have been independent for decades but retain the monarchy -- in tandem ceremonies on Sunday.

China's President Xi Jinping, who is not expected to attend the funeral, said he was willing to "expand friendly exchanges and mutually beneficial cooperation" as he congratulated Charles on ascending to the throne.

The queen's record 70 years on the throne were a constant during a turbulent time for Britain, from a world of post-war deprivation and the loss of its empire, to more recent upheavals like Brexit and the coronavirus pandemic.

Charles's coronation, an elaborate ritual steeped in tradition and history, will take place in the same historic surroundings of Westminster Abbey, as it has for centuries, on a date to be fixed.

© Agence France-Presse