Dramatic footage shows a crowd of teenagers screaming and shouting at the Arndale amid a 'disturbance' which saw a 16-year-old boy stabbed in the chest.
A large group of teenagers can be seen at the entrance to the Next store in the shopping centre.
A fight then appears to break out inside, before dozens of youths rush out into the street.
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Police were called at about 7.20pm on Friday (January 28) following a report of a stabbing inside a shop.
The victim was knifed during a 'disturbance' between two groups of teenagers, Greater Manchester Police said.
He was taken to hospital, but his injuries are fortunately 'neither life-changing nor threatening'.
Two other teenagers suffered minor injuries and were taken to hospital.
They have since been discharged.
The group believed to be responsible for the attack fled the scene before police arrived. No arrests have been made.
Speaking to the Manchester Evening News, the victim's father said his son was set upon by a gang of strangers and was 'lucky to be alive'.
He said his son was inside the Arndale with his friends when he was approached by a 'random' girl at about 7pm.
"They were just going for a bite to eat and to do shop shopping," he said.
"A girl asked for directions to a shop and he pointed it out. She went and brought all these lads over. There were about 20 of them.
"They asked if he was being cheeky and he said he had not done anything wrong. It all escalated from there.
"One of them kicked him in the neck then all hell broke loose.
"They went into Next and these other lads ran through the security and set about them again, throwing bottles.
"They cornered them and this lad ran over and stabbed him in the chest."
The man said he received a phone call informing that his son had been stabbed shortly before 7.30pm.
"It was horrendous," he said.
"That phone call comes and it's the worst experience of your life.
"The doctor said a millimetre either way and it would've hit an artery and we'd have been having a different conversation.
"He's lucky to be alive."
Images from the scene showed several police vans and an ambulance outside Next, at the junction of Withy Grove and Corporation Street.
Inspector Glen Rees of GMP's City of Manchester division said: "I fully understand and sympathise with the worry and concern that incidents such as this can cause for the wider public, especially in such a busy area on a Friday evening.
"I would like to stress that we are treating this as an isolated incident and we do not believe there to be any ongoing wider threat to the general public.
"Thankfully the young man who was stabbed has not suffered any life changing injuries but violence such as this will not be tolerated and a full investigation is currently underway to establish the full circumstances and identify those involved.
"Our enquiries are ongoing but I would appeal to anyone who may have witnessed the assault or has any information to come forward and assist us with our investigation.
"This was a busy part of the city centre so I am confident there will be people out there who can help us identify those responsible."
Anyone with information - or video footage - is asked to contact police via LiveChat at www.gmp.police.uk, or via 101 quoting incident 2488 of 28/01/21.
Details can be passed to Crimestoppers, anonymously, on 0800 555 111.
