The King will be presented with the Honours of Scotland at a National Service of Thanksgiving at St Giles' Cathedral in Edinburgh on Wednesday.

The festivities - which are part of Royal Week - will also include a People's Procession, a Royal Procession, a 21-gun salute, and a flypast by the Red Arrows.

Lorna Slater and Patrick Harvie, who are both ministers in the Scottish government as well as co-leaders of the Scottish Greens, have announced they turned down invitations to attend the church ceremony.

Mr Harvie, MSP for Glasgow, instead plans to speak at a rally outside Holyrood organised by Scottish republican group Our Republic.

Police Scotland said it has been engaging with protest groups ahead of the service.

Mr Harvie said: "There are many people in Scotland who regard the monarchy as a tiresome spectacle and a symbol of values we don't hold.

"I will be proud to speak at the Our Republic rally and to stand with others who want to build a more democratic society where power and wealth belongs to the people rather than being passed down as an inheritance.

"That is just one reason why I support Scottish independence. It will give us the opportunity to ask the big questions about how we are ruled and to build a fairer and more equal society."

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Ms Slater, MSP for Lothian, added that in a 21st century Scotland, the monarchy "is nothing to celebrate".

She added: "It is an out-of-date and undemocratic institution.

"How can we justify a system that allows one family to enjoy so much unearned wealth and privilege at a time when millions of people have so little?

"Scotland can be a modern and democratic republic with an elected and accountable head of state.

"I want every child in Scotland to know they live in a genuine democracy and that they can achieve the highest office, regardless of which family they come from."

The royal celebrations on Wednesday will begin around lunchtime.

First Minister Humza Yousaf, who is himself a republican, will be attending the ceremony.

He previously said: "I will attend the service at St Giles' Cathedral and I look forward to representing the people of Scotland at this historic event."