May 22 (UPI) -- A suicide bomber killed 22 people and injured 59 others Monday night at an Ariana Grande concert in Manchester, British police said.
The bomber died in what police were treating as a terrorist incident, Chief Constable Ian Hopkins of the Greater Manchester Police said in a statement.
"We believe the attacker was carrying an improvised explosive device, which he detonated, causing this atrocity," he said.
Hopkins said authorities were trying to determine whether the bomber was acting alone or part of a network. He confirmed children were among the dead.
Out of respect for the victims, Prime Minister Theresa May and opposition leader Jeremy Corbyn agreed to suspend campaigning for Britain's June 8 general election until further notice.
"We are working to establish the full details of what is being treated by the police as an appalling terrorist attack," May said. "All our thoughts are with the victims and the families of those who have been affected."
"from the bottom of my heart, i am so so sorry. i don't have words."
Panicked spectators fled Manchester Arena after what several concertgoers described as a huge bang after the last song. The arena, built in 1995, has a capacity of 21,000 spectators but it was not clear how many people attended the show.
"We saw young girls with blood on them, everyone was screaming and people were running," Sasina Akhtar, told The Manchester Evening News.
"It shook," Hannah Dane told The Guardian, "then everyone screamed and tried to get out."
Emma Johnson told BBC Radio Manchester she and her husband were waiting at the arena to pick up their children, ages 15 and 17, when glass suddenly exploded.
"It was near to where they were selling the merchandise," she said. "There was a blast and then a flash of fire afterwards. There were bodies everywhere."
Bomb disposal units were dispatched to the arena after reports of an explosion. After securing the area, police said they carried out a "precautionary controlled explosion" that confirmed abandoned items were clothing, not suspicious items.
"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," Hopkins said.
Grande's international tour, promoting her 2016 album Dangerous Woman, was scheduled to continue Thursday at the O2 Arena in London.
"We mourn the lives of children and loved ones taken by this cowardly act," Scooter Braun, Grande's manager, said in a statement. "We ask all of you to hold the victims, their families, and all those affected in your hearts and prayers."
The incident evoked the November 2015 terrorist attacks in Paris, which included a deadly assault on an concert arena. In a tribute to the Manchester victims, the Eiffel Tower lights went out at midnight.
The U.S. Department of Homeland Security said in a statement it was monitoring the situation and had "no information to indicate a specific credible threat involving music venues in the United States."