Video footage showed thousands of people fleeing in tears from the venue, many covered in blood, after the Ariana Grande concert finished.
Armed officers surrounded the venue and bloodied concertgoers were pictured being helped by emergency services outside the gig.
Evie Brewster, who attended the concert, told MailOnline: ‘Ariana Grande had just finished her last song and left the stage when a huge explosion sounded.
‘Suddenly everybody started screaming and running for the exit.
‘We could hear the police and ambulance sirens. It was terrifying.
‘There were thousands of people trying to get out at once. They were all screaming and crying. The whole place smelt smokey and burnt.
‘The explosion sounded like it was inside the building somewhere.’
Manchester’s Victoria station, which backs onto the arena, has been evacuated and all trains cancelled.
Panicking at Victoria Station after @ArianaGrande concert. Hope everyone is all safe and well. pic.twitter.com/6Q5WNXFkFO
— Zach Bruce (@Zach_bruce) May 22, 2017
Greater Manchester Police said: ‘Emergency services are currently responding to reports of an explosion at Manchester Arena.
‘There are a number of confirmed fatalities and others injured.
‘Please AVOID the area as first responders work tirelessly at the scene. Details of a casualty bureau will follow as soon as available.’
Jonathan Yates, 24, from the Wirral, who attended the gig, told MailOnline: ‘The concert had finished and the lights came on almost instantly. There was a bang, a weird bang. There were lots of balloons but I thought to myself that can’t be a balloon, that’s not normal.
‘We were sat on the floor level and it came from the higher seats, people were running and screaming. Everyone stopped and I turned to my friend and said ‘we need to run’. Everyone was running and screaming and then when we got out it felt a bit more OK.
‘I heard five or six bangs that sounded like gunshots. When we got outside people were outside, crying and on their phones.
‘You don’t think it’s something that’s going to happen when you go…it was such a nice, fun concert.’
Nick Schurok, 28, from Manchester, told MailOnline: ‘Ariana Grande had just finished the concert and the lights came on. Everyone started leaving. I was on the floor and at the back of the arena people started exiting through the tunnels.
‘There was a bang in the left tunnel and everyone went to the middle tunnel. Then about two minutes later, there was another bang. The bang was so loud and crowds of people were running. There were lots of children and families there.’
Another witness Jenny Brewster told MailOnline: ‘We were exiting the building when it happened. We’d headed towards the main doors as Ariana was performing the last song because we wanted to beat the crowds, but – as we made our way there – a wall of security men blocked it and told us to go the other way.
‘Seconds later they shouted ‘RUN!’ and the explosion happened right behind them. Hundreds of people were running and screaming. Those men saved our lives.’
Catherine Macfarlane told Reuters: ‘We were making our way out and when we were right by the door there was a massive explosion and everybody was screaming.
‘It was a huge explosion – you could feel it in your chest. It was chaotic. Everybody was running and screaming and just trying to get out of the area.’
Majid Khan, 22, said: ‘I and my sister, along with a lot of others were seeing Ariana Grande perform at Manchester Arena, and we were all exiting the venue when around 10.40-10.45pm-ish a huge bomb-like bang went off that hugely panicked everyone and we were all trying to flee the arena.
‘It was one bang and essentially everyone from the other side of the arena where the bang was heard from suddenly came running towards us as they were trying to exit Trinity Way and that was blocked so everyone was just running to any exit they could find as quickly as they could.
‘Everyone was in a huge state of panic, calling each other as some had gone to the toilet whilst this had gone off, so it was just extremely disturbing for everyone there.’
Another concert-goer Laura, 22, told MailOnline: ‘There was a woman leaning against a car in the car park with her head down, covered in blood and a little girl being lifted away by paramedics. There were quite a few people injured in the car park.’
Her friend, Livvy, 22, added: ‘we saw the explosion happen. Bits of it hit me. My first thought was, ‘that’s a bomb’.
‘It was just when we were leaving. We saw a flash of light and smoke.
‘We’re really shaken up. If we had been there moment earlier we would have been caught up in it rather than seeing it.’
Oliver Jones, 17, was at the concert with his 19-year-old sister.
He said: ‘I was in the toilet and heard a loud bang just after the concert had finished and people had started to leave.
‘The bang echoed around the foyer of the arena and people started to run.
‘I seen people running and screaming towards one direction and then many were turning around to run back the other way.
‘Security was running out as well as the fans and concert goers.
‘Reports of blood and people injured.’
He added: ‘In so much shock and panic. You see this on the news all the time and never expect it to happen to you. I just had to run and make sure me and my sister were safe.’
Suzy Mitchell, 26, whose flat is opposite the venue, reported a huge bang rocking the neighbourhood.
She told the Press Association: ‘(I) just heard a huge bang from my bed, came out to the front of my apartments (we’re on the top floor so have perfect view) and everyone was running away in big crowds.
‘The bang was so big I heard it from my room which is at the back of the apartment blocks.
‘Currently lots of emergency services going to and from. But can’t see anything substantial as of yet except fleeing people and lots of cars.
Erin McDougle, 20, from Newcastle said: ‘There was a loud bang at the end of the concert. The lights were already on so we knew it wasn’t part of the show.
‘At first we thought it was a bomb. There was a lot of smoke. People started running out. When we got outside the arena there were dozens of police vans and quite a few ambulances.’
A group of young men from Sheffield said they had seen at least five people covered in blood and others being carried out by bouncers.
‘Ariana Grande had just gone behind the curtain and the lights came up when there was this massive bang and a big cloud of smoke. I saw five people with blood all down them,’ said one.
Sophie Tedd, 25, from Darlington, said the noise and smoke seemed to come from the tiered seating stage right. ‘We were sitting on that side then suddenly there was this big bang in the block next to us,’ she said.
‘Everyone started screaming and we nearly got trampled on. There was a burning smell.’
A witness inside the venue, who gave only her first name, Ashley, told Sky News: ‘After the explosion, the staff in the Arena were telling us to follow the exit and go outside.
‘At first we did not think it was serious as we could not see any smoke but when we went outside we could see it was more serious.
‘There were loads of police turning up telling people to move away from the site.
‘Now there are a few people around still trying to get home – they are stuck because Manchester Station is closed.
‘I’ve not seen so many police in my life.’
Sasina Akhtar said: ‘We were in the lower tier and there was an explosion behind us at the back of the arena.
‘We saw young girls with blood on them, everyone was screaming and people were running. There was lots of smoke.’
Kindhearted locals also took to social media to offer their help to people who had attended the concert.
Kim Corbett wrote: ‘If anyone needs picking up please let me know. I live in Bury but I’m happy to help any way I can. God bless those hurt tonight.’
Vicky Fraser added: ‘If anybody needs somewhere to stay I will pick them up…can meet them as close as I can get to town.’
There are reports on social media that up to 50 unaccompanied children have been taken in to Manchester Holiday Inn and are being looked after by adults.
Paula Robinson posted on Facebook: ‘We have taken as many kids as we can to Holiday Inn we will keep them safe and stay with them.’
Former Manchester United footballer Rio Ferdinand said: ‘Just heard the news what’s happening in Manchester… hope everyone is safe and sound!’
Labour leader Jeremy Corbyn tweeted: ‘Terrible incident in Manchester. My thoughts are with all those affected and our brilliant emergency services.’
A spokesman for Greater Manchester Police said: ‘Emergency services responding to serious incident at Manchester Arena. Avoid the area. More details will follow as soon as available.’
A British Transport Police spokesman said: ‘We are aware of an incident at Manchester Arena. We have officers at the scene and will provide further updates as soon as possible.’
US pop singer Grande was performing her Dangerous Woman European tour at Manchester Arena when the incident happened.
Later this week, she is scheduled to perform in London, followed by concerts in Belgium, Poland and Germany.
Read more: http://www.dailymail.co.uk/news/article-4531940/Emergency-services-rush-Manchester-Arena.html#ixzz4hr1fzBZm