Relatives are using social media to hunt for missing loved ones, after Twenty-two people, including children, were killed and 59 injured in a suicide attack at Manchester Arena, state media reports.
The blast happened at 22:35 BST on Monday at the end of a concert by US singer Ariana Grande.
Police have set up an emergency telephone number in response to the attack. It is: 0161 856 9400.
Greater Manchester Police said the lone male 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.
The explosion happened in the foyer of the arena shortly after Ariana Grande left the stage.
Grande, a 23-year-old American TV teen actress-turned-singer has a strong following among teenage girls and children.
She tweeted: “broken. from the bottom of my heart, i am so so sorry. i don’t have words.”
from the bottom of my heart, i am so so sorry. i don’t have words.
— Ariana Grande (@ArianaGrande) May 23, 2017
Flags are flying at half mast in Downing Street and political parties have suspended general election campaigning.