Twenty-two people, including children, have been killed and 59 injured in a suicide attack at Manchester Arena.
Fifty-nine others were injured in the blast at 10.33 pm local time on Monday at the end of a concert by US singer Ariana Grande.
Greater Manchester Police are treating the incident as a terror attack.
Police said the lone male attacker, who detonated an improvised explosive device was also killed in the blast.
Police said they believe at this stage that one man carried out the attack, but are trying to establish if he was working alone of as part of a network. Nobody has claimed responsibility.
Sixty ambulances attended the incident and those wounded are now being treated at six hospitals around the city.
The Manchester Arena, where the blast occurred, is one of the largest concert venues in Europe with a capacity of 21,000.
“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,” said Chief Constable Ian Hopkins, of Greater Manchester Police on Tuesday.
“The attacker, I can confirm, died at the arena. We believe the attacker was carrying an improvised explosive device which he detonated causing this atrocity.
“We would ask people not to speculate on his details or to share names. There is a complex and wide ranging investigation underway.”
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.”
Thousands of people traveled to Manchester for the concert.
Sophie Tedd, from Darlington, a town about 110 miles away in northeastern England, told the Northern Echo, ” suddenly there was this big bang in the block next to us. Everyone started screaming and we nearly got trampled on. There was a burning smell.”
Robert Tempkin, 22, from Middlesbrough, a town in northern England, told the Echo: “Everyone was screaming and running, there were coats and people’s phones on the floor. Some people were screaming they’d seen blood but other people were saying it was balloons busting or a speaker had been popped.”
Following the incident, Grande tweeted: “Broken. from the bottom of my heart, i am so so sorry. i don’t have words.”
May will hold an emergency government meeting Tuesday. All campaigning ahead of the June 8 general election has been suspended.