Sixteen children and teacher Gwen Mayor were murdered by gunman Thomas Hamilton when he opened fire on a gym class at Dunblane Primary School on March 13, 1996.
The massacre in the Perthshire town shocked the nation and led to the UK enforcing some of the strictest firearms legislation in the world.
On Saturday, First Minister wrote on her Twitter account: “This day, 25 years ago, was one of the darkest and most heartbreaking in Scotland’s history.
“Thinking today of 16 little children, their teacher and all those who still live with the pain.
Prime Minister Boris Johnson said on social media that “we must never forget” the victims of Dunblane.
In a post on Twitter, the Prime Minister wrote: “The brutal murder of 16 primary school children and their teacher in Dunblane 25 years ago shocked the world.
“We must never forget all those who lost their lives on that terrible day.
“Today my thoughts are with the bereaved, the survivors, and the whole Dunblane community.”
Scottish Conservative leader Douglas Ross said: “Today we remember those who so tragically lost their lives during the Dunblane massacre 25 years ago.
“The painful memories of this heartbreaking day remain with us all and my thoughts go out to all those commemorating lost loved ones today.”
Police Scotland also posted a tribute on Twitter.
A spokesperson wrote: “Today we remember those we lost during the Dunblane Primary School shooting 25 years ago.
“Our deepest sympathies are with all of those affected by this horrific incident. Not just today, but always.”
Despite churches being closed due to the current coronavirus restrictions, Rev Colin Renwick, minister at Dunblane Cathedral, will hold worship online on Sunday and remember the victims in prayer.
Mr Renwick said: “Many people in Dunblane will be marking this particular anniversary as they mark March 13 every year – quietly, privately and with respect for those who lost their lives in the tragedy of 25 years ago.
“They will also be remembering those whose grief will always be deepest, and the people who still, in one way or another, bear scars.
“Some will light a candle in their home, spending time in quiet reflection, prayer and remembering.
“For those who lost someone in the tragedy, every day will be one of remembering in some way, and the anniversaries that will be just as poignant for them will be the birthdays of those they have lost, as they ponder what might have been.
“As is the case every year, the people lost, and those affected most profoundly, will be remembered in prayers in churches throughout the community, including Dunblane Cathedral, on the Sunday closest to March 13.
“Sadly, because of restrictions associated with the Covid-19 pandemic, Dunblane Cathedral, in common with all church buildings and other historic properties, is currently closed, and worship is being held online.”
Prayers during Dunblane Cathedral’s online service will include words inscribed on the memorial to the tragedy in the south aisle of the Cathedral: “Hear the Truth. Unless your hearts are changed and you become like little children, you will not enter the Kingdom of heaven at all.”