An eight-year-old girl was among the dead, and it is understood many under-16s were injured at the concert.
The pop fan, from Radcliffe , was reportedly leaving the venue when he was targeted by the attacker.
A local police force tweeted: "As the news comes in, the sympathies and condolences to the familes of Georgina Callander, Saffie Rose Roussos and John Atkinson #RIP"
Tributes were paid by the local adult dance troupe, Freak Dance Radcliffe, for whom Mr Atkinson danced competitively.
A message on Facebook from the group read: “Today is an amazingly sad day! ‘We have lost a member of our dance family."
They described him as a “happy gentle person” and a “real pleasure to teach”.
“He was a true friend, not just to our staff but many of the parents and students from the school. Our thoughts are with the family at the very sad and hard time!”
Lee Paul posted on Facebook: “Sleep tight John Atkinson. Thoughts and prayers with all your family and the other 21 people who lost there lives last night.”
Talie Andrea wrote: “Heartbroken for the Atkinson family at this sad time never would I imagine this happening so close to home. Rest in paradise John you beautiful soul.”
A GoFundMe has been launched by the local community and it has raised almost £2,000.
Well-wishes wrote: "We are trying to help his family in any way possible at this tragic time. I know all us Radcliffe people can pull together and help this local family out.
"Please donate generously as we all know funeral cost are expensive and will help the family at this sad time! John was one one in a million and loved by so many!! A true gentleman. R.I.P John thoughts and prayers with you family and all of the other victims effected by this tragedy"
Saffie-Rose RoussosSaffie-Rose Roussos died from her injuries at the concert on Monday night.
The headteacher at her school, Chris Upton, said: "Saffie was simply a beautiful little girl in every aspect of the word. She was loved by everyone".
In a statement released this afternoon, Tarleton Community Primary School headteacher, Chris Upton, said the news was "heartbreaking".
He added: "Saffie was simply a beautiful little girl in every aspect of the word.
"She was loved by everyone and her warmth and kindness will be remembered fondly.
"Saffie was quiet and unassuming with a creative flair.
"Our focus is now on helping pupils and staff cope with this shocking news and we have called in specialist support from Lancashire County Council to help us do that.
"We are a tight-knit school and wider community and will give each other the support that we need at this difficult time."
Saffie-Rose's mother and sister, Lisa and her older sister Ashlee are being treated for shrapnel injuries in separate hospitals.
Kate Tinsley, whose daughter Jessica was a friend of Saffie at Tarleton Community Primary School, near Preston, had earlier told The Sun: "Everybody is worried, the whole village. Everybody is in bits waiting for news, just some news that she's okay, she's alive."
Saffie-Rose was at the concert with her mother Lisa and her older sister Ashlee, who are both reportedly being treated in hospital.
Georgina CallanderThe first named victim of the Manchester terror attack was Georgina Bethany Callander, an 18-year-old Ariana Grande superfan who was excited to see her idol on Monday night.
Ms Callander had met Ariana Grande in 2015, and posted excitedly about the time she met her star on Instagram.
She attended Runshaw college in Lancashire.
"Georgina Callander was a former Bishop Rawstorne pupil studying with us on the second year of her Health and Social Care course.
"Our deepest sympathies, thoughts and prayers go out to all of Georgina’s family, friends, and all of those affected by this loss.
"We are offering all available support possible at this tragic time, including counselling with our dedicated student support team."
When she met Ariana Grande two years ago, she wrote: "Thank you for everything my love I miss you."
Before the concert, Ms Callander wrote on Twitter: "SO EXCITED TO SEE YOU TOMORROW."
She knew she was attending the show in 2016, and wrote of how she couldn't wait to hear Ariana Grande sing.
The student was a big fan of music and film, and has posted many proud pictures of herself meeting her idols on social media.