A man has been detained under the Mental Health Act after five people were stabbed at the Arndale centre.
The 40-year-old was arrested on suspicion of terrorism offences following this morning's attack.
Tonight police say he's been 'compulsorily detained' under the Mental Health Act after being assessed by specialist doctors.
In a statement police said: "The investigation will continue in order to fully understand the motives behind the attack.
"There is not believed to be any wider threat to the communities of Greater Manchester and the attacker is believed to have acted alone."
There were reports a man targeted people 'randomly' at around 11.15am this morning.
Witnesses reported shoppers fleeing in terror.
One told the Manchester Evening News: "He had a knife, he was shouting, he was running after us. I was scared for my life. Wow. It was scary. I was 100 metres away.
"He came out, he went back in the Arndale for 50 seconds. He came out and walked down the road shouting.
"I didn’t know what was going on. We all came outside. I went to Exchange Square then I turned and saw him.
"Everyone was running, shouting. He came out running after people.
"I’m still scared right now to walk in this street."
The suspect is thought to be British and lives in Manchester.
Detectives believe the man attempted to attack several people, including two unarmed PCSOs who tried to detain him.
He was eventually arrested by armed officers when PCSOs asked for backup.
Three people - a 19-year-old woman, another woman and a man in his 50s - were stabbed before being taken to hospital.
A woman in her 40s was not stabbed, but was assessed by paramedics.
Another woman received a 'superficial knife injury'.
Speaking at a press conference this afternoon Assistant Chief Constable Russ Jackson said: "We do not know the motivation for this terrible attack.
"It appears random, it was certainly brutal, and of course extremely frightening for anyone who witnessed it.
"This is bound to bring back memories of the awful events of 2017.
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"We will have increased patrols, including armed patrols in the city centre this weekend. This is to reassure people but we do not believe there is a wider threat at this time and we are hoping to return the city to normality by tomorrow morning."
Anyone with images or footage from the scene is asked to upload it via http://www.ukpoliceimageappeal.co.uk/ and anyone with information that could assist the investigation should call 0161 856 0394.
