One year on from the attack, Prime Minister Theresa May leaves a message on a "Tree of Hope" in Manchester.
"Today my thoughts and prayers are with those who were lost on that bad night, their loved ones who have so bravely battled to rebuild their lives; those who have courageously fought to overcome physical injury or mental scars; our first responders and emergency services and those volunteers and professionals who are continuing to help this community heal", May wrote.
Take That's Never Forget followed as members of the crowd embraced and held their hands in the air - before The Beatles' All You Need Is Love rounded things off.
The service, attended by first responders, civic leaders and some of the scores injured in the bombing, led the minute of silence at 2.30pm (2330 AEST), which was also marked at British government buildings nationwide.
Ariana Grande marks anniversary of Manchester bomb attack
Well-wishers have also been encouraged to share messages of tribute, solidarity and love, and hang them on the Trees of Hope trail throughout the city, the Manchester Evening News reported.
"It was created to strike at the heart of our values and our way of life in one of our most vibrant cities, with the aim of breaking our resolve and dividing us".
She wrote: 'So wish i were there with u all today. u have no idea. love you so v much'.
Jack also recited words that Ariane Grande said in the aftermath of the tragedy past year.
Mayor Andy Burnham said the anniversary is a day to come together.
They will join more than 3,000 singers from local choirs at the Manchester Together - With One Voice event in the city's Albert Square from 7.30pm to 9pm.
Some laid bouquets of flowers in St. Ann's Square.
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