Police have apologised for making a fake Islamist suicide bomber use a "religious phrase" during a counter-terror exercise in Manchester.

The simulated attack started on Monday night, when a man dressed in black walked into the Trafford Centre and shouted at the crowd.

Moments later an explosion rocked the food hall and hundreds of volunteers, wearing ear defenders and safety glasses, dropped to the floor and ran into shops and cafes screaming.

Emergency services take part in a simulated terror attack at the Trafford Centre, Manchester. Police later apologised for the use of an Islamic religious phrase (Getty) (Getty Images)

Many wore make-up to simulate serious injuries and others shouted for help in The Orient food court as the sound of gunfire rang out and armed officers moved in.

A man playing the part of a terrorist repeatedly shouted “Allahu Akbar” (“God is great”) before acting out the explosion.

Community groups and activists condemned the use of “stereotypes” for the exercise, with some raising concerns it would fuel anti-Muslim prejudice.

In response to criticism, Greater Manchester Police’s assistant chief constable Gary Shewan said the decision was “unacceptable” and apologised for any offence caused.

In pictures: Terror attack exercise in Manchester Show all 7 1 /7 In pictures: Terror attack exercise in Manchester In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre The emergency services and volunteers take part in a simulated terror attack at the Trafford Centre on 10 May, 2016 in Manchester, England. PA In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre Emergency forces and shoppers take part in a simulated terror attack at the Trafford Centre on 10 May, 2016 in Manchester, England. Getty Images In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre The emergency services and volunteers take part in a simulated terror attack at the Trafford Centre on 10 May, 2016 in Manchester, England. Getty Images In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre The emergency services and volunteers take part in a simulated terror attack at the Trafford Centre on 10 May, 2016 in Manchester, England. Getty Images In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre Emergency services and volunteers take part in a simulated terror attack at the Trafford Centre in Manchester on 10 May 2016. Getty Images In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre Emergency services and volunteers take part in a simulated terror attack at the Trafford Centre in Manchester on 10 May 2016. Getty Images In pictures: Terror attack exercise in Manchester Counter-terror exercise at the Trafford Centre People playing the role of injured shoppers react during an exercise at the Intu Trafford Centre in Trafford, Manchester, on May 10, 2016. PA

“The scenario for this exercise is based on a suicide attack by an extremist Daesh [Isis] style organisation and the scenario writers have centred the circumstances around previous similar attacks of this nature, mirroring details of past events to make the situation as real life as possible for all those involved,” he said in a statement.

“However, 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 with Islam.

“We recognise and apologise for the offence that this has caused.”

Dr Erinma Bell, who was made an MBE for her anti-gun campaign work in Manchester, was among those criticising the decision.

“We need to move away from stereotypes if we want to achieve real learning,” she tweeted. “A terrorist can be anyone.”

Anti-islamophobia group the Community Safety Forum called the use of the phrase “Allahu Akbar” offensive and said it was not necessary to make the scenario real.

Volunteers lay down during the false attack, which was criticised for increasing anti-Muslim hate crime (Getty) (Getty Images)

“This sort of thing panders to stereotypes and further divides us,” a spokesperson added. “It will increase anti-Muslim hate crime.”

But many Twitter users were defending the simulation, saying it was justified to imitate the events of the Brussels and Paris attacks.

Police stressed that there was no specific threat to the Trafford Centre, which is the second-largest in the UK.