All general election campaigning has been suspended, including the SNP’s manifesto launch, following the Manchester bombing.
Flags at the Scottish Parliament flew at half mast following the attack, which killed 22 people.
Prime Minister Theresa May has chaired a meeting of the UK Government’s emergency Cobra committee and will now travel to Manchester.
The Conservative leader said the suicide bomber deliberately chose the place where he could cause “maximum carnage” when he detonated a bomb at a pop concert.
Mrs May said “many” children and young people were among the 22 dead and 59 injured in the attack.
She confirmed that police and security services believe they know the identity of the man responsible and are now working to establish whether he was acting alone or as part of a group.
Speaking outside Downing Street after chairing a meeting of the Government’s Cobra emergency committee, Mrs May condemned the “cowardice” of the attacker and hailed those who rushed to help, who had shown “the spirit of Britain … a spirit that through years of conflict and terrorism has never been broken and will never be broken”.
She vowed: “The terrorists will never win and our values, our country and our way of life will always prevail.”
First Minister Nicola Sturgeon is chairing the Scottish Government’s resilience committee.
The SNP leader said: “My thoughts are with the victims, their families and all those who have been affected by this barbaric attack in Manchester.
“The Scottish Government is working with Police Scotland and the UK Government to ensure that we have a full understanding of the developing situation.
“I will convene a meeting of the Scottish Government’s Resilience Committee this morning to receive an update and to consider any implications for Scotland.”
Home Secretary Amber Rudd said the Manchester explosion was a “barbaric” attack on some of the “most vulnerable in our society”.
She said the intention of the attack was to “sow fear” but stressed that it would not succeed.
In a statement, she said: “I know that some people will only just be waking up to the news of the horrific attacks in Manchester last night.
“This was a barbaric attack, deliberately targeting some of the most vulnerable in our society – young people and children out at a pop concert.
“My thoughts and prayers go out to the families and the victims who have been affected, and I know the whole country will share that view.
“I’d like to pay tribute to the emergency services who have worked throughout the night professionally and effectively – they have done an excellent job.
“Later on this morning, I will be attending COBRa, chaired by the Prime Minister, to collect more information – to find out more – about this particular attack, and I can’t comment any more on that at the moment.
“The public should remain alert but not alarmed. If they have anything to report, they should approach the police.
“But I have two further things to add.
“The great city of Manchester has been affected by terrorism before. Its spirit was not bowed; its community continued.
“This time it has been a particular attack on the most vulnerable in our society – its intention was to sow fear – its intention is to divide. But it will not succeed.”
Rt Rev Dr Derek Browning, the Moderator of the General Assembly if the Church of Scotland, lead a gathering in prayer and a minute’s silence for the victims of the attack when the Assembly opened on Tuesday morning.
He said: “When the news of this appalling and brutal act in Manchester came to us, most of us will have been stunned.
“That young people and children, with others, could be the subject of what Police are now treating as a premeditated act of violence is beyond comprehension. There is no cause, political or religious, that justifies actions of senseless brutality, anywhere or at any time.
“Today the General Assembly of the Church of Scotland offers its prayer and deepest concern to all who have been caught up in this action. The young people and their families and friends, the emergency and security services, and the people of that great city of Manchester.
“We pray for them and send our sincerest wishes of peace to come in this heart-rending situation.”
Scottish political reaction
Holyrood business has been altered on Tuesday afternoon, to include an urgent statement to the chamber from Ms Sturgeon.
STV News has postponed a planned debate between Scotland’s political leaders.
A spokeswoman for the broadcaster said: “In light of events in Manchester and the suspension of general election campaigning, STV has taken the decision to postpone its Scottish party leaders debate planned for Wednesday evening.”
Conservative leader Ruth Davidson said: “This is devastating news and all my prayers go out today to the families of those who were killed and injured.
“I can only imagine the pain they are feeling and their heartbreak is shared across the country.
“It goes without saying that our political campaigning will cease today.
“Terrorism has once against struck our country and, once again, we are faced with a sense of disbelief that someone could be capable of carrying out such an appalling act.
“We all stand with the people of Manchester.
“We also all know that this wonderful vibrant city will not be defeated by this terrorist act.
“The courageous work of our emergency services and the generosity and help offered by ordinary people after the attack are the values that define us.
“We have faced down terror before, and we will do so again.”
Scottish Labour leader Kezia Dugdale said: “This is a barbaric and sickening attack, targeted at young and vulnerable people enjoying a night at a concert.
“It is a heartbreaking moment for our country, and our thoughts are with the families and friends of those who have lost their lives and with those who are injured.
“Across the UK we are today grieving for the people of Manchester. I pay tribute to the dedication of the brave emergency service workers who ran into danger.
“We have all been moved by the actions of ordinary people who opened their doors, cared for scared youngsters, provided transport to concert-goers, and are giving blood at donor banks to help those injured.
“This great city is today demonstrating to the world the true spirit of Manchester.”
Scottish Liberal Democrat leader Willie Rennie said: “I am horrified by the deaths and injuries in Manchester.
“My deepest sympathies are with the victims, and with families who have lost loved ones, as well as those desperately waiting for news.”
Commons cannot be recalled after attack
With every seat in the House of Commons vacant there are no MPs and therefore no parliament to recall in the aftermath of the Manchester bombing.
Dissolution of the last parliament occurred on May 3 to enable the June 8 General Election.
Successful candidates will either swear the oath of allegiance or make an affirmation during the week after the election and the next parliament opens on June 19.
But the Government remains in place during dissolution as, despite not being MPs, the Prime Minister is appointed by the Queen and ministers appointed by the Queen on the advice of the PM.
This enables ministers to look after their departments until a new administration is formed.
Parliament was last recalled on June 20 during the EU referendum campaign to pay tribute to Jo Cox, the Labour MP who was murdered in her Batley and Spen constituency.
A vote to approve air strikes against terror group Islamic State in Iraq led to a recall in September 2014, with MPs returning to Parliament during what is traditionally the time for party conferences.
Such recalls were possible as the Commons was temporarily not sitting rather than having been dissolved.
Following the Westminster terror attack on March 22, MPs pressed ahead with scheduled business in the Commons on the following day.
They also paid tribute to those who died and were injured when Islamist extremist Khalid Masood launched a car and knife attack on Westminster Bridge and the Houses of Parliament.
