Commuters spotted the 22-year-old kneeling on a Metrolink tram platform at Victoria station – next to the city’s Arena – between 6pm and 6.30pm, four hours before he returned to detonate his lethal device.
A source said Abedi seemed on a reconnaissance mission of the venue and was “quietly mumbling to himself and rocking backwards and forwards” and apparently praying.
“There is CCTV of Abedi at the venue earlier in the evening while he carried out a dry run,” said the unnamed source.
“He looked vacant and emotionless but deep in thought.
People noticed him but clearly had no inkling of what must have been going through his mind at the time
“People noticed him but clearly had no inkling of what must have been going through his mind at the time. He must have been steeling himself to go through with the bomb.”
A total of 22 people – including seven children – were killed in the attack at the end of an Ariana Grande concert – the worst terrorist atrocity in Britain since the July 7 bombings of 2005.
More than 100 people were injured and 52 remain in hospital including 19 still in intensive care.
According to reports he was again seen praying on the platform before taking an elevator to a raised walkway and ambling across it to the Arena.
Manchester bomber Abedi was seen "praying and psyching himself up" hours before the attack
CCTV images of the killer inside the lift show him wearing a padded jacket and baseball cap.
Other footage appears to show Abedi hours earlier at a convenience store near the £75-a-night short-let city centre flat where it is thought he stayed before the attack.
SAS troops raided the property on Wednesday amid fears he may have set up booby-trap bombs.
Police last night released an image of Abedi carrying a distinctive blue suitcase on the day of the attack and appealed for information.
Abedi was seen carrying a blue suitcase on the day
Det Chief Superintendent Russ Jackson from the North West Counter Terrorism Unit said they were keen to track his whereabouts between May 18 and May 22.
He said: “We know he visited the Wilmslow Road area of Manchester and was also seen in Manchester city centre with the blue suitcase.
“If you have any details about the suitcase we need you to get in touch and let us know.
“The public should not approach the case if they see it but contact police immediately on 999.”
CCTV footage captured Abedi at a convenience store
Anyone with information should call the Anti-Terrorist Hotline in confidence on 0800 789 321, he added.
Earlier shocked passengers watched armed police lead a man from a packed double decker bus at Rusholme in the heart of the city’s famous Curry Mile around 4.30pm.
Greater Manchester Police said it had executed a warrant at an address in the area and a search was ongoing.
Families and close friends of the victims last night made a private visit to the Arena, while hundreds marked a week since the tragedy by gathering to remember the dead and injured.
Manchester bombing: Investigation so far Wed, May 24, 2017
The investigation so far into the Manchester bomb attack that killed at least 22 people, with more than 60 injured after Salman Abedi detonated a bomb in the Manchester Arena, at 10:30pm Monday, 22 May 2017
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Handout photo courtesy of Alex Finnie, of men wearing body armour during a raid of a block of flats in Blackley, north Manchester, following the attack on Manchester Arena
At Trafford Town Hall, Councillor John Holden told those gathered: “We will not be defeated by acts of hatred or destruction. We will not be cowed.”
Crowds also gathered at St Ann’s Square where flowers, teddy bears and football scarves cover the plaza alongside hand-written notes for the dead.
Eliot Leeming, 20, whose brother Jonathan, 17, was at the concert but uninjured, said: “I’m here for the families who lost somebody.”
Abedi was wearing a padded jacket and baseball cap
Mr Leeming, from Rossendale, Lancs, added: “I’m just grateful I’m not mourning my dead brother.”
Manchester resident Helen Hayward 25, said: “It’s very sombre, people are very quiet and respectful. I think it’s respectful and remembering it, but also a defiance and continuing to be normal and not be defeated by it.”
The “We Love Manchester Emergency Fund” for victims and their relatives yesterday reached £5.76million.