A double rainbow appeared over Buckingham Palace moments after news of the Queen's death was announced.

Another rainbow appeared at Windsor Castle shortly after, with some emotional Brits calling it "a sign" from the Queen herself that "she has really left us".

It came as crowds anxiously waited to hear the news outside the palace gates, with some saying the Queen "left it" for the nation.

A double rainbow even appeared over the Victoria memorial, as some saw it as a sign the Queen is finally reunited with her beloved husband Prince Philip.

One Twitter user wrote: "There was a double rainbow outside Buckingham Palace. Some here view it as a representation of the Queen and Prince Philip."

It comes as Buckingham Palace announced today that the Queen has passed away aged 96 at Balmoral Castle in Scotland, early this morning NZT.

One person wrote on Twitter: "The rainbow at Windsor Castle made me cry. The rainbow Queen sent us a sign.'

Another said: "A rainbow breaks out, as the Union Jack is lowered to half-mast at Windsor tonight. A remarkable image. Farewell, Ma'am."

Tourists gather near a rainbow over the Queen Victoria Memorial as the Queen's death is announced. Photo / Getty Images

Britons gathered at the Queen's estates since Buckingham Palace's earlier announcement that doctors were becoming "concerned" over her health.

The royal family were seen rushing to Balmoral to visit the Queen before she died.

A Buckingham Palace spokesperson said: "The Queen died peacefully at Balmoral this afternoon. The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow.

The Queen's death will see Britain and the rest of the Commonwealth enter a 10-day mourning period, as millions of her subjects across the globe come to terms with her passing.