Queen Elizabeth visited the Royal Manchester Children's Hospital, where some of the casualties have been treated. A minute's silence was observed in honour of the victims at a square in central Manchester and in other places in Britain.
England's National Health Service said a total of 116 had been injured in the attack, with 75 admitted to hospital. Twenty-three remained under close care.
Soldiers and bomb disposal experts rushed to a street in the south of the city after a call to police, but it turned out to be a false alarm.
The bombing, which took place at the Manchester Arena indoor venue just after the end of a concert by U.S. pop singer Ariana Grande, was the deadliest in Britain since July 2005, when 52 people were killed in attacks on London's transport network.
The Manchester attack has caused revulsion across the world because it targeted children and teenagers, who make up the bulk of Grande's fan base. The victims range from an eight-year-old schoolgirl to parents who had come to pick up their children.
A total of eight people are in custody in connection with the attack. British media have reported that one of them is Abedi's brother but police have not confirmed that.
Abedi's father and younger brother were arrested in Tripoli in Libya, where the family originally come from.
Manchester's police chief said on Wednesday Abedi was part of a network, and media have reported that authorities suspect he received help constructing the bomb and planning the attack.
Anger in Manchester as mosques targeted after terror attack
Obama 'heartbroken' by Manchester attack
Former United States President Barack Obama said at a Berlin reunion with German Chancellor Angela Merkel Thursday he was "heartbroken" by a suicide bombing that killed 22 people in Manchester.
"We can see the terrible violence that took place just recently in Manchester... it's a reminder that there is great danger of terrorism and people who would do great harm to others just because they're different," Obama told a crowd at the German capital's Brandenburg Gate.
He and Merkel had sent a joint message of condolence to the families of those killed in the Monday attack during a concert by US pop star Ariana Grande, he added.
Obama addresses terror events in Germany
"We had a chance backstage to send a message to the people of Manchester about how heartbroken we are by the loss of life," Obama said.
Some 70,000 people had gathered at the central Berlin landmark to see Obama reunited with Merkel for the Evangelical Church's biennial gathering, German public television reported.
