Agencies (Qasioun) – A Suicide attack occurred at the English Manchester Arena on late Monday, which led to kill 22 people including children and injure 59 others, during a concert by the US singer Ariana Grande.
Greater Manchester Police said the suicide attacker, who died in the blast, was carrying an improvised explosive device which he detonated.
Sixty ambulances attended the incident and those wounded are now being treated at six hospitals around the city.
Chief Constable Ian Hopkins said it was "the most horrific incident" Greater Manchester had ever faced.
He said the "fast-moving investigation" was now working to establish whether the attacker "was acting alone or as part of a network".
Eyewitnesses described seeing metal nuts and bolts among the debris, and spoke about the fear and confusion that gripped those caught up in the events.
Home Secretary Amber Rudd said it was "a barbaric attack, deliberately targeting some of the most vulnerable".
The prime minister is to chair a meeting of the government's emergency Cobra committee at around 09:00.
The blast occurred close to the entrance to Victoria train and tram station. The station has been closed and all trains cancelled.
Police also carried out a precautionary controlled explosion in the Cathedral Garden area of the city at about 01:32. The force later confirmed it was not a dangerous item.
Greater Manchester Mayor Andy Burnham said the city would "pull together", adding: "That's what we are. That's what we do. They won't win."