Police have confirmed they are treating the explosion incident at Manchester Arena on Monday night following a concert by American pop singer Ariana Grande as a terrorist attack.
It is the deadliest such incident on British soil since 2005. It is believed many of the victims were teenagers.
This is what we know so far:
Speaking to the BBC, an eyewitness gave this account of what happened:
The apparent bombing in Manchester at the Ariana Grande concert is the second terror attack to hit England in two months. In March, five people were killed and more than 50 injured when a man drove into pedestrians on Westminster Bridge in central London. His vehicle then crashed into the gates of parliament. The attacker was shot dead by police. Nobody has been charged in connection with that incident.
London Mayor Sadiq Khan says security measures are being stepped up in the capital following events overnight in Manchester.
“I am in constant contact with the Metropolitan police, who are reviewing security arrangements in London. Londoners will see more police on our streets,” he said.