Here is how events unfolded:
6pm - Doors open at Manchester Arena in the north of the city centre. US pop singer Ariana Grande is on the bill for a sell-out concert. Fans, many of them teenage girls, excitedly share selfies as they wait for the show to begin.
7.30pm - Show’s scheduled start time. After a performance from support act BIA, an American rapper, Grande takes the stage.
10.30pm - Show’s scheduled finish. Thousands of fans begin to file out of the arena’s four exits.
A “huge bomb-like bang” is heard at the arena.
Witnesses describe being knocked from their feet by an explosion and seeing dozens of injured, possibly dead, people including children lying on the floor. Others describe panic as concert-goers run for exits.
10.33pm - Greater Manchester Police (GMP) are called to reports of an explosion at Manchester Arena. Dozens of emergency services vehicles stream into the area.
10.55pm - Police urge people to stay away from the area as responders deal with a “serious incident”.
11.46pm - Police say there have been a number of confirmed fatalities.
1.10am - Nineteen people are confirmed dead and around 50 others injured following the suspected explosion police say is being treated as a terrorist incident.
1.35am - A controlled explosion is carried out on a suspicious item in the Cathedral Gardens area near Manchester Arena. It is later confirmed to be abandoned clothing.
2.15am - Prime Minister Theresa May says her thoughts are with the victims and families of those affected in “what is being treated by the police as an appalling terrorist attack”.
:: - Shortly before 4am Ariana Grande tweets that she is “broken”, adding: “From the bottom of my heart, I am so so sorry.”
7am - GMP Chief Constable Ian Hopkins gives a statement. He says the death toll has risen to 22, including children, with 59 injured. He confirms police are treating the attack as a terrorist incident and believe it was carried out by a suicide bomber detonating an improvised explosive device.
Shortly after 9am US President Donald Trump expresses his “deepest condolences” and calls those responsible “evil losers”.
Around 11am, after chairing a Cobra meeting, Mrs May says the attacker has been identified by security services, but does not release details. She says the “callous” attack was “among the worst terrorism we have experienced in the United Kingdom”.
Less than an hour later, GMP says it has arrested a 23-year-old man in South Manchester in connection with the incident.
12.12pm - The Queen releases a statement expressing her “deepest sympathy” to all those affected by the explosion, adding that the whole nation had been shocked by the “death and injury”.
Before 1pm Islamic State claims responsibility for the atrocity.
In the early afternoon names of the victims begin to emerge, including Georgina Callander, and eight-year-old Saffie Roussos.