King Charles III was proclaimed Canada's head of state on Saturday at a ceremony that included heraldic trumpeting, a 21-gun salute and a moment of remembrance for his mother, Queen Elizabeth II.

Prime Minister Justin Trudeau arrived at Rideau Hall at about 10 a.m. local time with his youngest son Hadrien and laid flowers at a makeshift memorial for the queen, who died Thursday.

He and members of the federal cabinet and Privy Council met prior to the ceremony as part of the protocol needed to formally proclaim the new sovereign.

The Prime Minister asked Gov. Gen. Mary Simon for permission to proceed, and after she said yes both signed the order-in-council and the proclamation for the accession.

The solemn moment unfolded at the same table used by Queen Elizabeth II during her first official visit to Canada in October 1957, and was followed by a round of applause from those gathered in the Rideau Hall ballroom.

Dr. Samy Khalid, the chief herald of Canada, led a procession outside moments later. After a fanfare played on heraldic trumpets, he read the proclamation of the accession in both official languages. As he spoke, an artillery salute was fired by members of the Royal Canadian Armed Forces.

"We (the Governor General and the Privy Council) proclaim that His Royal Highness Prince Charles Philip Arthur George is now by the death of our late sovereign, Charles III, by the grace of God of the United Kingdom, Canada and his other realms and territories, King, head of the commonwealth, defender of the faith to whom we acknowledge faith and allegiance," said Khalid.

"Long live the King," he concluded, with those gathered repeating the phrase.

The Canadian flag was raised to mark the accession of the new sovereign, but was immediately lowered to half-mast as mourning for the queen continues.

The accession ceremony at Rideau Hall comes as the federal government prepares a series of events to commemorate the legacy of Queen Elizabeth II.

Protocol calls for 10 days of mourning following the Queen's death, but the rules around the actual funeral are not as rigid. British officials announced on Saturday that the queen's state funeral will take place at Westminster Abbey on Sept. 19.

This report by The Canadian Press was first published Sept. 10, 2022.

— With files from Michael Tutton in Halifax.