Anti-terror police swooped on the Trafford Centre in a training exercise to test their response to a Paris or Brussels-type Islamic State attack.
It was an attempt to show how the authorities would react to a terror incident in a public place.
Officers from the North West Counter Terrorism Unit, armed with their guns, were drilling their training techniques and counter-terror tactics during the exercise at the Trafford Centre in Manchester, starting at midnight.
But critics have attacked the project on social media as it showed a fake bomber, detonate explosives, seconds after shouting “God is greatest” in Arabic.
Dr Erinma Bell wrote on Twitter: “We need to move away from stereotypes if we want to achieve real learning. A terrorist can be anyone.”
Iiyas Nagdee added: “Stupid decision by @gmpolice to decide attackers should be seen as Muslim.”
It led to Assistant Chief Constable Garry Shewan of Greater Manchester to respond: “This was unacceptable and I apologise for the offence caused.”
In a statement the force later said: “On reflection we acknowledge that it was unacceptable to use this religious phrase immediately before the mock suicide bombing , which so vocally linked this exercise to Islam.
“We recognise and apologise for the offence this has caused.”
Dramatic scenes saw the suicide bomber detonate explosives followed by volunteers screaming for help and getting down on the floor as if it were a real attack.