A number of people have died and others are injured after a reported explosion at Manchester Arena during a pop concert.
Witnesses reported hearing a "huge bang" at the venue shortly after US singer Ariana Grande's gig finished on Monday evening.
Greater Manchester Police said there are a "number of confirmed fatalities and others injured" and emergency services are at the scene after reports of an explosion.
The area around the arena was swamped with police and emergency services and approach roads were closed.
Witnesses said they heard two loud bangs inside the arena coming from the area of the bars.
One fan at the concert with his sister described how the apparent explosion happened as fans were leaving the arena.
Majid Khan, 22, said: "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."
Oliver Jones, 17, who attended with his 19-year-old sister, said: "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."
Manchester's Victoria station, which backs on to the arena, has been evacuated and all trains cancelled.
National Rail said in an online statement: "Emergency services are dealing with an incident at Manchester Arena. As Manchester Victoria is located near the arena, the station has been evacuated and all lines closed.
"Trains are currently unable to run to/from Manchester Victoria. Some trains will be cancelled throughout or start/terminate at alternative stations. Disruption is expected to continue until end of the day."
British Transport Police said: "Officers are at Manchester Arena following reports of an explosion within the foyer area of the stadium at 10.30pm this evening.
"Emergency services are at the scene and we are working to establish more information regarding the explosion and will provide further updates as soon as possible."
A spokesman for American singer Ariana Grande, who was performing at the arena, told the BBC she was okay.