Here is what we know so far about the terrorist attack at Manchester Arena that targeted young concert-goers.
:: Suicide bomber Salman Abedi, 22, detonated an improvised explosive device killing 22 people and injuring up to 64. The injured - including 12 under the age of 16 - were being treated at eight hospitals across Greater Manchester. Abedi died at the arena.
:: The explosion took place at Manchester Arena as people began streaming from the doors after a show by American singer Ariana Grande.
:: Security services are investigating whether Manchester-born Abedi, whose family are reported to be of Libyan origin, acted alone or was part of a network. Islamic State claimed responsibility for the attack.
:: A 23-year-old was arrested in south Manchester in connection with the incident on Tuesday.
:: The first victim was named as college student Georgina Callander. Eight-year-old schoolgirl Saffie Roussos was also killed.
:: All national General Election campaigning was suspended and Prime Minister Theresa May described the bombing as being "among the worst terrorism we have experienced in the United Kingdom". US President Donald Trump later branded the attackers "evil losers" and Greater Manchester metro mayor Andy Burnham called the atrocity "an evil act".
:: Metropolitan Police Commissioner Cressida Dick announced that extra police officers have been put on duty in London in the wake of the attack.
:: A controlled explosion was carried out on Tuesday afternoon, as part of the investigation, at an address in Fallowfield.
:: Mrs May raised the security threat level to the highest possible rating of critical, meaning another atrocity is expected imminently, saying a "wider group of individuals" could have been involved in the blast.
:: Armed troops are deployed to guard "key locations" such as Buckingham Palace, Downing Street, the Palace of Westminster and embassies. The Palace of Westminster is closed to the public and the Changing the Guard ceremony at Buckingham Palace is cancelled to redeploy police officers.
:: On Wednesday Greater Manchester Health and Social Care Partnership said 64 people are being treated, with 20 in critical care in hospital.
:: Home Secretary Amber Rudd said Abedi was known to the intelligence services "up to a point", while French interior minister Gerard Collomb said Abedi is believed to have travelled to Syria and had "proven" links with the Islamic State terror group. Mr Collomb told French television that both British and French intelligence services had information that Abedi had been in Syria.
:: Three men are arrested in south Manchester, meaning that by Wednesday a total of four people have now been arrested as part of the inquiry into the atrocity.
:: A Polish couple who had gone to the venue to collect their daughters were revealed to be among those killed and PR manager Martyn Hett is the latest person to be named as a victim.
:: Greater Manchester Police Chief Constable Ian Hopkins said officers are carrying out "extensive searches" across Manchester, adding that "it's very clear this is a network we are investigating".
He also confirmed that a serving officer had been killed. The BBC reported that the officer was with her husband and two children who were all injured, the husband critically.
:: The Government activated Operation Temperer, providing up to 3,800 troops to support the police in their security operations. Ms Rudd said that 984 military personnel have been deployed.
:: Armed police and officers raided a block of flats on Granby Row close to Manchester Piccadilly Station in connection with the arena attack.