Explosions in Ariana Grande concert in Manchester, UK kills undetermined number of people.

There are a number of confirmed deaths at Manchester Arena following a reported explosion at an Ariana Grande concert, police have said.

Twitter users reported thousands of concert goers fled the arena  covered in blood and crying, although it is not immediately clear what the reported “loud bangs” were.

The noises were heard towards the end of the show, with witnesses claiming on social media they believed the bangs were a “gun shot” or a “bomb.

A concert-goer named Josh told the BBC there was huge panic and confusion as people tried to flee the arena, with some people suggesting a stampede might have caused injury and death as people tried to flee.

“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 tweet from a writer said: “A friend works in A&E – huge balloons filled with gas popped and there was a stampede because everyone thought it was a bomb!”

One fan leaving the concert described how the loud bangs resonated as fans were leaving the venue, 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 people in their teens and twenties.

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.”

Liverpool City Region metro mayor Steve Rotheram told the BBC he had been at the concert with his wife and daughters and had seen a number of people lying on the ground as he desperately searched for his family.

He said there were “a good 20 to 30 people lying injured” close to the box office, on the way into the arena.

Emergency services are said to be in attendance at the venue close to Manchester Victoria station with police helicopters reported to be circling overhead.

There is no official confirmation of any casualties.

Police have warned people to stay away from the arena while investigations take place.

“Police responded to reports of an incident at Manchester Arena. Please stay away from the area,” Greater Manchester Police said on Twitter.