An explosion has reportedly hit Manchester Arena during a pop concert.

Witnesses reported hearing a "huge bang" at the venue during an Ariana Grande gig and police have warned people to stay away from the area.

Greater Manchester Police tweeted: "Police responded to reports of an incident at Manchester Arena. Please stay away from the area."

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."

One fan at the concert described how the explosion hit the venue as fans were leaving the building.

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.

The Herald:

"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."

Witnesses reported helicopters were circling above the scene after reports of the blast.

The Herald:

Footage showed lines of ambulances heading towards the venue, while Ms Mitchell said it appeared the main surrounding road had been closed.

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."

Liverpool City Region metro mayor Steve Rotheram tweeted: "My 2 daughters caught up in the Manchester explosion at the arena. They are thankfully safe, but I fear for others."

The area around the arena was swamped with police and emergency services. Approach roads have been closed by police.

Witnesses said they heard two loud bangs inside the arena and coming from where the bars are located.