The wounded have been treated in hospitals across the city, with 12 children under the age of 16 among them.
Several people are still missing, such as teenagers Laura MacIntyre and Eilidh MacLeod, from Barra in the Outer Hebrides, in Addition to 15-year-old Olivia Campbell and Chloe Rutherford, 17, and Liam Curry, 19.
Scotland’s First Minister Nicola Sturgeon said police were in contact with Laura and Eilidh’s households, including: “It is hard for any of us to imagine the anguish which their families are going through right now.
“They’re in our thoughts.”
In a statement in Downing Street on Tuesday, the prime minister said the bombing was a “callous terrorist attack” that targeted “defenceless young people”.
She stated the security services believe they know the attacker’s identity but are not yet able to affirm it.
It is the worst terrorist attack in the UK because the 7 July bombings in 2005, where 52 people were killed by four suicide bombers.
So-called Islamic State has stated – via IS channels on the messaging program Telegram – it had been behind the Manchester attack, but this hasn’t been verified.
The BBC understands the perpetrator was British or from the United Kingdom.
Greater Manchester Police Chief Constable Ian Hopkins stated the “fast-moving investigation” was now working to establish whether the attacker “was acting alone or as part of a network”.
Officers have carried out raids in two properties, one in Whalley Range and one in Fallowfield, in which a controlled explosion has been carried out.
In its most recent statement the force stated the area around the stadium remained cordoned off but stated it wanted to “remind people that Manchester will not be defeated – the city is open for business.”
In other developments:
Relatives are using social media to hunt for missing loved ones, and an emergency number – 08000960095 – has been put up
Theresa May chaired a meeting of the government’s crisis Cobra committee and is now visiting Manchester
Extra armed officers will be deployed to Wembley and Twickenham on Saturday, while safety at all forthcoming events and places in England are under inspection. The Met Police has also raised the numbers of officers on duty Throughout the funding
Authorities have established a support centre at Manchester City’s Etihad Stadium, accessibility Gate 11, for anyone who wants assistance in tracing loved ones
The Queen extended her “deepest sympathy” to all those affected and other senior royals have stated they’re “shocked and saddened”; Pope Francis offered “heartfelt solidarity” with the sufferers and their families
Andy Holey, who’d gone to pick up his wife and daughter, stated: “An explosion went off and it threw me about 30ft from 1 pair of doors into another pair of doors.”
Emma Johnson, who proceeded to pick her up children, aged 15 and 17, stated: “The entire building shook. There was a blast and then a flash of passion afterwards. There were bodies everywhere.”
Teenager Abigail Walker, who had been in the concert, told the BBC: “I had to make sure I had my sister. I caught hold of her and pulled hard. Everyone was running and crying.
“It was absolutely terrifying.”
The explosion happened soon after US singer Ariana Grande had left the stage and also the 23-year-old actress-turned-singer, tweeted: “broken. From the bottom of my heart, I am so so sorry. I don’t have words”.
Analysis: Gordon Corera, BBC security correspondent
The united kingdom threat level has been judged to be acute for almost 3 years – which means an attack is considered highly probable.
But in recent months the tempo of counter terrorist activity has been increasing with – on average – an arrest every day.
After the attack in Westminster by Khalid Masood in March, police and security officials have been warning that further strikes were almost inevitable.
But they also thought that those were more likely to be low-tech between vehicles or knives. The fact that the Manchester attack included explosives will stress them.
It may not have been in the level of complexity seen in Paris in 2015, when several attackers sent out of Syria used firearms and suicide belts, but it is going to nevertheless have required preparation.
The blast happened close to the entrance to Victoria railway and tram station. The channel has been closed and most of trains cancelled.
Greater Manchester Mayor Andy Burnham stated the city would “pull together”, including: “That is what we are. That is what we do. They won’t win.”
The Manchester Arena is the city’s biggest indoor place with a concert capacity of approximately 21,000.
A spokesman for the stadium called the event “a senseless tragedy”, but praised the emergency services for their answer.
Authorities are inviting anyone with footage from the scene to upload it in ukpoliceimageappeal.co.uk or even ukpoliceimageappeal.com. Other information can be reported to the anti-terrorist hotline on 0800789321.