Prime Minister Theresa May called an emergency meeting with intelligence chiefs on the deadliest militant assault in Britain since four British Muslims killed 52 people in suicide bombings on London's transport system in July 2005.
Witnesses related the horror of the blast which prompted a stampede just as the concert ended at Europe's largest indoor arena.
"We ran and people were screaming around us and pushing on the stairs to go outside and people were falling down, girls were crying, and we saw these women being treated by paramedics having open wounds on their legs ... it was just chaos," said Sebastian Diaz, 19.
"It was literally just a minute after it ended, the lights came on and the bomb went off," Diaz said.
U.S. President Donald Trump described the attack as the work of "evil losers". German Chancellor Angela Merkel said it "will only strengthen our resolve to...work together with our British friends against those who plan and carry out such inhumane deeds.Read more at Reuters