Nicola Sturgeon has said it is "hard" to look back on this day six years ago when Scotland voted against independence.

The First Minister took to Twitter on Friday, marking six years since the 2014 referendum on September 18, 2014.

The 'No' side won in 2014, with 2,001,926 (55%) voting against independence and 1,617,989 (45%) voting in favour.

READ MORE: David Cameron urges PM to reject second independence referendum even if SNP wins Holyrood majority

Recent poll shave suggested Scots would vote in favour of independence if a second referendum was to be held in the future, and Ms Sturgeon said plans for another vote would be set out by the Scottish Government in a draft bill at Holyrood.

Taking to Twitter today, she said it is "hard" to look back on the result.

She wrote: "Hard to look back on this day in 2014 without a sad feeling of what might have been.

"I prefer to look forward with a firm belief in what will be. #indyref2 #Yes"

On Thursday, former PM David Cameron said Boris Johnson should reject a second independence referendum if the SNP wins a majority at next year's Holyrood election.

He said the UK government allowed the nationalists to set the terms in 2014 - and said it was not "appropriate" for there to be another ballot.

READ MORE: John Curtice: SNP majority means it would be difficult to avoid Indyref2 within three years

Speaking to Times Radio, he argued that Scotland had “asked for a once in a generation, once in a lifetime referendum”, and that he had accepted most of their demands when he was in power, including giving the vote to 16-year-olds.

But Scotland's leading pollster, Professor Sir John Curtice, previously said it would be difficult for the UK Government to avoid another independence referendum within two or three years if the SNP secures a majority at the next Holyrood election.