Here is the statement by Chief Constable Ian Hopkins in full.
"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.
"Families and many young people were out to enjoy a concert at the Manchester Arena and have lost their lives.
"Our thoughts are with those 22 victims that we now know have died, the 59 people who have been injured and their loved ones. We continue to do all we can to support them. They are being treated at eight hospitals across Greater Manchester.
"As you will appreciate this is a fast-moving investigation and we have significant resources deployed to both the investigation and the visible patrols that people will see across Greater Manchester as they wake up to the news of the events last night.
"This will include armed officers as people would expect and more than 400 officers have been deployed on this operation throughout the night.
"To remind you, we were called at about 10.33pm to reports of an explosion at the Manchester Arena. This was at the conclusion of the Ariana Grande concert.
"We then received more than 240 calls and emergency services responded very quickly to the scene. Emergency numbers have been established for anyone who is concerned for their loved ones who may not have returned home, these numbers are 0161 856 9400 or 0161 856 9900.
"We have been treating this as a terrorist incident and we believe at this stage the attack last night was conducted by one man. The priority is to establish whether he was acting alone or as part of a network.
"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 share names. This is a complex and wide ranging investigation.
"Our priority is to work with the National Counter-Terrorist Policing Network and UK intelligence services to establish more details about the individual who carried out this attack.
More on the incident in Manchester: