Twenty-two people have been killed and at least 59 people injured in a terrorist bombing during an Ariana Grande concert at Manchester Arena.

Children are known to be among the dead.

It is the worst terror attack in the UK since 56 people were killed in the 7 July London bombings in 2005.

Footage showed thousands of people fleeing the arena in a panic after an explosion ripped through the foyer as people milled out of the arena at 10.33pm.

An injured woman is helped by emergency services in Manchester (London News Pictures)

Eyewitnesses said the explosion was heard outside the auditorium after the artist had finished her show and left the stage.

Casualties were taken to five hospitals throughout the city and victims described being thrown by the blast that scattered nuts and bolts across the floor.

The Prime Minister has condemned the "appalling" attack and General Election campaigning has been suspended.

Ariana Grande said on Twitter she was "broken" by the devastating attack.

Announcing that the death toll had risen overnight, Greater Manchester Police chief constable Ian Hopkins said: "What I can confirm is that there are children among the deceased."

He said: "This has been the most horrific incident we have had to face in Greater Manchester and one that we all hoped we would never see.

"Families and many young people were out to enjoy a concert at the Manchester Arena and have lost their lives."

Mr Hopkins said investigators believed the attack was conducted by one man who died at the scene, although detectives are working to establish if he "was acting alone or as part of a network".

Manchester explosion in pictures Show all 37 1 /37 Manchester explosion in pictures Manchester explosion in pictures People running down stairs as they attempt to exit the Manchester Arena after a blast, where U.S. singer Ariana Grande had been performing, in Manchester Twitter/@ZACH_BRUCE/ via REUTERS Manchester explosion in pictures Helpers attend to people inside the Manchester Arena after a suspected suicide bomber detonated an explosive device at the end of an Ariana Grande concert, killing 22 people PA wire Manchester explosion in pictures Armed officers guard outside a hotel near the Manchester Arena following reports of an explosion, in Manchester, Britain EPA Manchester explosion in pictures Police officers are seen outside the Manchester Arena, where U.S. singer Ariana Grande had been performing, in Manchester, northern England Reuters Manchester explosion in pictures MANCHESTER, ENGLAND - MAY 23: Police escort members of the public from the Manchester Arena on May 23, 2017 in Manchester, England. An explosion occurred at Manchester Arena as concert goers were leaving the venue after Ariana Grande had performed. Greater Manchester Police have confirmed 19 fatalities and at least 50 injured. (Photo by Christopher Furlong/Getty Images) Getty Images Manchester explosion in pictures MANCHESTER, ENGLAND - Emergency services arrive close to the Manchester Arena on May 23, 2017 in Manchester, England. There have been reports of explosions at Manchester Arena where Ariana Grande had performed this evening. Greater Manchester Police have have confirmed there are fatalities and warned people to stay away from the area. (Photo by Dave Thompson/Getty Images) Getty Images Manchester explosion in pictures MANCHESTER, ENGLAND - MAY 23: Police escort members of the public from the Manchester Arena on May 23, 2017 in Manchester, England. An explosion occurred at Manchester Arena as concert goers were leaving the venue after Ariana Grande had performed. Greater Manchester Police have confirmed 19 fatalities and at least 50 injured. (Photo by Christopher Furlong/Getty Images) Getty Images Manchester explosion in pictures Medics deploy at the scene of a reported explosion during a concert in Manchester, England on May 23, 2017. British police said early May 23 there were "a number of confirmed fatalities" after reports of at least one explosion during a pop concert by US singer Ariana Grande. Ambulances were seen rushing to the Manchester Arena venue and police added in a statement that people should avoid the area / AFP PHOTO / Paul ELLIS (Photo credit should read PAUL ELLIS/AFP/Getty Images) AFP/Getty Images Manchester explosion in pictures Police and fans close to the Manchester Arena, after reports of an explosion Getty Images Manchester explosion in pictures There have been reports of explosions at Manchester Arena where Ariana Grande had performed Getty Images Manchester explosion in pictures Police deploy at scene of explosion in Manchester, England, at a concert in Manchester Arena AFP/Getty Images Manchester explosion in pictures Police stand by a cordoned off street close to the Manchester Arena Getty Images Manchester explosion in pictures Police deploy at scene of explosion in Manchester, England AFP/Getty Images Manchester explosion in pictures Police deploy at scene of a reported explosion during a concert in Manchester, England, on May 23, 2017. British police said early May 23 there were "a number of confirmed fatalities" after reports of at least one explosion during a pop concert by US singer Ariana Grande. Ambulances were seen rushing to the Manchester Arena venue and police added in a statement that people should avoid the area AFP/Getty Images Manchester explosion in pictures An ambulance drives away from the Manchester Arena, where U.S. singer Ariana Grande had been performing, in Manchester Reuters Manchester explosion in pictures Police escort members of the public from the Manchester Arena in Manchester, England. Getty Images Manchester explosion in pictures A woman sits in the street in a blanket near the Manchester Arena as police guard the area following reports of an explosion, in Manchester, Britain EPA Manchester explosion in pictures Two women wrapped in thermal blankets stand near the Manchester Arena, where US singer Ariana Grande had been performing, in Manchester Reuters Manchester explosion in pictures A Royal Logistic Corps (RLC) bomb disposal robot is unloaded outside the Manchester Arena following reports of an explosion, in Manchester. At least 19 people have been confirmed dead and others 50 were injured, authorities said. It is being treated as a terrorist incident until police know otherwise EPA Manchester explosion in pictures A Royal Logistic Corps (RLC) bomb disposal robot is unloaded outside the Manchester Arena following reports of an explosion, in Manchester EPA Manchester explosion in pictures Members of the public receive treatment from emergency service staff at Victoria Railway Station close to the Manchester Arena on May 23, 2017 in Manchester, England. There have been reports of explosions at Manchester Arena where Ariana Grande had performed this evening. Greater Manchester Police have have confirmed there are fatalities and warned people to stay away from the area Getty Images Manchester explosion in pictures Armed police after a suspected terrorist attack at the Manchester Arena at the end of a concert by US star Ariana Grande left 19 dead PA wire Manchester explosion in pictures Emergency services arrive close to the Manchester Arena in Manchester Getty Images Manchester explosion in pictures An amoured police vehicle patrols near Manchester Arena in Manchester Getty Images Manchester explosion in pictures A man carries a young girl on his shoulders near Victoria station in Manchester AFP/Getty Images Manchester explosion in pictures Police officers stand at the Miller Street and Corporation Street Crossroads, in front of the Manchester Arena in Manchester, England Getty Images Manchester explosion in pictures Police block a road near to the Manchester Arena in central Manchester, England AP Manchester explosion in pictures Armed police patrol near Victoria station in Manchester, northwest England. Twenty two people have been killed and dozens injured after a suspected suicide bomber targeted fans leaving a concert of US singer Ariana Grande in Manchester Getty Images Manchester explosion in pictures Police forensic officers leave the Manchester Arena as they investigate the scene of an explosion in Manchester Getty Images Manchester explosion in pictures A forensic officer collects evidence on a walkway between Victoria station and Manchester Arena following a deadly terror attack in Manchester, Getty Images Manchester explosion in pictures A woman and a young girl wearing a t-shirt of US singer Ariana Grande talks to police near Manchester Arena following a deadly terror attack in Manchester, Getty Manchester explosion in pictures epaselect epa05982725 Susan Walton and daughter Katie, 10 (pictured), who attended the concert of Ariana Grande at the Manchester Arena, are seen in Manchester, Britain, 23 May 2017. According to a statement released by the Greater Manchester Police on 23 May 2017, police responded to reports of an explosion at Manchester Arena on 22 May 2017 evening. At least 19 people have been confirmed dead and around 50 others were injured, authorities said. The happening is currently treated as a terrorist incident until police know otherwise. According to reports quoting witnesses, a mass evacuation was prompted after explosions were heard at the end of US singer Ariana Grande's concert in the arena. EPA/NIGEL RODDIS EPA Manchester explosion in pictures Mayor of Greater Manchester Andy Burnham and Manchester City Council Leader Sir Richard Leese speak to the media outside Manchester Town Hall after a suicide bomber killed 22 people, including children, as an explosion tore through fans leaving a pop concert in Manchester Dave Higgens/PA Wire Manchester explosion in pictures The media gather behind a police cordon in Manchester Getty Images Manchester explosion in pictures Flowers left close to the Manchester Arena, the morning after a suicide bomber killed 22 people, including children, as an explosion tore through fans leaving a pop concert in Manchester Danny Lawson/PA Wire Manchester explosion in pictures Ariana Grande concert attendees Karen Moore and her daughter Molly Steed, aged 14, from Derby, leave the Park Inn where they were given refuge after last night's explosion at Manchester Arena Getty Manchester explosion in pictures Signs saying 'We love Manchester' are displayed in a window in Manchester, England Getty Images

Andy Burnham, the Greater Manchester metro mayor, said the attack was an "evil act".

Speaking on Tuesday morning the former Labour MP said: "It is hard to believe what has happened here in the last few hours, and to put into words the shock, anger, and hurt that we feel today.

"These were children, young people and their families that those responsible chose to terrorise and kill.

"This was an evil act."

He added: "We are grieving today, but we are strong. Today it will be business as usual, as far as possible in our great city."

Ariana Grande said she had 'no words' to express her feelings (AP)

Concert goer, Josh Elliot, told the BBC there was pandemonium and confusion as people tried to flee the scene, some reportedly covered in blood and many in tears.

He said: "She finished her last song .. and we heard like a really basey bang, and all I can remember is just everyone ... was just running out... people were covered in blood, some people were having a fight, it was quite scary."

One fan leaving the concert described how the bangs ripped through the arena, which has a capacity of 21,000. It is not known how many people were attending the concert, but the majority of the American pop star's fans are young females in their teens and twenties.

"The lights came on after the gig and people were starting to leave. As I turned to the left there was an explosion. It was about 40ft behind us near one of the exits. We just thought it was people messing about then it happened again. Another explosion sounded.

“Then we saw the smoke. Everyone just fled. Some people were injured. We saw blood on people when we got outside. People were just running all over the place.

“People have said it was a speaker or balloons but it wasn’t. It was explosions.”

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."

He said there were "a good 20 to 30 people lying injured" close to the box office just outside the main arena.

"Whoever's done it has done it on a kids' concert," he said.

Another eyewitness said he was thrown "30 feet in the air" by the force of the explosion which was reported to have shaken the entire building.

Another witness, Karen who was at the concert with her husband and children described the pandemonium as thousands tried to escape the venue after the explosion sound was heard.

"It was just chaos... nobody was organising anybody to do anything."

She added that she saw a woman in a wheelchair being pushed over as people desperately tried to get out after someone shouted there had been a bomb.

Liverpool City Metro Mayor Steve Rotheram said on Twitter that his two daughters had been at the concert but had made it home safely. He thanked the taxi driver who had assisted them, and offered his sympathies to other parents waiting anxiously for news of their children.

Police warned people to stay away from the arena while investigations continued before they put out a statement confirming the number of fatalities shortly after 1am.

Police confirmed a bomb disposal squad carried out a controlled explosion of a suspect device around 1am, although this turned out to be benign.

Prime Minister Theresa May said in a statement: "We are working to establish the full details of what is being treated by the police as an appalling terrorist attack.

"All our thoughts are with the victims and the families of those who have been affected."

Other politicians including Labour leader Jeremy Corbyn, Greater Manchester Mayor Andy Burnham and MP Lucy Powell expressed their shock and offered condolences on Twitter.

Manchester City football club tweeted: "It's with great sadness we hear of the terrible events at the Arena. Our hearts go out to all affected and to our city's emergency services.''

Offers of help and shelter for people stranded in the city began flooding in on social media.

Greater Manchester Chief Constable Ian Hopkins said at a press conference in the early hours of Tuesday morning that the force is working with other officials to investigate the circumstances of the explosion.

He urged people to avoid the area while the investigation continues.

He said: "We are currently treating this as a terrorist incident until we know otherwise. We are working closely with the national counter-terrorism policing network and UK intelligence partners.

"This is clearly a concerning time for people but we are doing all we can, working with local and national agencies to support those affected and gather information about what happened last night."

A police hotline to assist those concerned about loved ones who may have been caught up in the explosion should call 0161 856 9400.