Greater Manchester Police have confirmed 22 people died and 59 have been injured following an "explosion" at the Manchester Arena.
An update from the police this morning said the death toll had risen from 19 to 22 and children are among the dead. The attacker also died in the explosion.
Witnesses described hearing a "huge bang" just after 10.30pm following a concert by US singer Ariana Grande.
Police carried out a controlled explosion on a suspect device several hours after the blast.
Chief Constable Ian Hopkins, of Greater Manchester police, provided an update this morning, confirming there are children among the dead though he did not have detail to hand.
We have been treating this as a terrorist incident and we believe that while 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 belive the attacker was carrying an improvised explosive device, which he detonated, causing this atrocity.
Police have advised anyone needing help after the incident to go to Etihad Stadium, access gate 11.
They have also asked people to avoid the area otherwise so that they can deal with the incident more effectively.
Anyone who needs help or assistance after last night's incident at Manchester Arena help is available at the Etihad Stadium access Gate 11— G M Police (@gmpolice) May 23, 2017
The emergency number for those concerned about loved ones is 0161 856 9400.
Network Rail said train lines out of nearby Manchester Victoria station were blocked.
Network Rail (@networkrail) May 23, 2017
In a statement, the British Transport Police said:
Officers are at Manchester Arena following reports of an explosion within the foyer area of the stadium at 10.30pm this evening.
Emergency services are at the scene and we are working to establish more information regarding the explosion and will provide further updates as soon as possible.
Please avoid the area whilst emergency services continue to respond to this incident. No trains or trams are running from Manchester Victoria station.
Prime Minister Theresa May has said her thoughts were with those affected by "what is being treated by the police as an appalling terrorist attack".
She will chair an emergency Cobra meeting later this morning.
The Conservatives, Labour, Liberal Democrats and SNP have confirmed today's election campaigning has been suspended in the wake of last night's attack.
Labour leader Jeremy Corbyn tweeted, paying tribute to the emergency services for their "bravery and professionalism", saying that today "the whole country will grieve for the people who have lost their lives".
I am horrified by the horrendous events in Manchester. My thoughts are with families and friends of those who have died and been injured. pic.twitter.com/QoCXH8qPYW— Jeremy Corbyn (@jeremycorbyn) May 23, 2017
Ariana Grande also tweeted after the explosion.