A book of condolence has been opened at Holyrood for the late Tory MSP Alex Johnstone.

Flags at the Scottish Parliament flew at half mast in memory of the North East Scotland politician, who died at the age of 55 after a short illness.

MSPs from across the chamber paid tribute to the MSP, who had been in the Scottish Parliament since it was established in 1999, during First Minister's Questions.

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First Minister Nicola Sturgeon said: "In his passing, the Scottish Parliament has lost one of its great personalities.

"He will be sorely missed across this chamber and my thoughts, all of our thoughts today, are with Linda, the rest of his family, and indeed with all of his colleagues."

Liberal Democrat leader Willie Rennie said: "He was a mischievous, humorous and engaging man, and I know that the whole chamber will miss Alex Johnstone."

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Scottish Labour leader Kezia Dugdale said: "This is indeed a sombre day for parliament, so on behalf of Scottish Labour let me extend our condolences to the family and friends of Alex Johnstone.

"He had a reputation as a proud and devoted family man, a great character and as a politician respected widely across this chamber."

Scottish Greens co-convener Patrick Harvie said: "We've all enjoyed many debates with Alex over the years, enjoyed them not least when we disagreed - which, let's face it, was probably most of the time - but he always took that role in a spirit of good humour and respect, and we will miss him."

Thanking MSPs for their comments, Conservative leader Ruth Davidson said: "We are all in mourning right now.

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"I do have to tell the chamber that Alex wouldn't want me to talk about him, he'd want me to get stuck in to the record of this government."

Holyrood's Presiding Officer Ken Macintosh added: "On behalf of Parliament, could I thank all the party leaders for their thoughtful and touching remarks following the death of Alex Johnstone, our colleague.

"As a mark of respect, our flags will be flying at half-mast today.

"There will be an opportunity for members to pay their own tributes and mark of respects in a motion of condolence, when that is scheduled.

"There will also be a book of condolence available after First Minister's Questions today. I know that members and staff will wish to add their names."