Anti-terror police swooped on a shopping centre in a staged training exercise which featured a mock suicide bomber detonating a device.
Armed officers drilled their training techniques and counter-terror tactics to test their response to a Paris or Brussels-type attack on civilians during the exercise at the huge Intu Trafford Centre shopping complex on the outskirts of Manchester.
Around 800 people were involved in the role-play exercise which started at midnight at the entrance to The Orient food court when a man dressed all in black walked in and shouted at the crowd.
Moments later an explosion rocked the food hall and volunteers - wearing ear defenders and safety glasses - dropped to the floor.
Many were made up to look as if they had horrific injuries and others screamed out as if in pain.
Smoke filled the entrance to the food court and some of the volunteers ran from restaurants, as if they were trying to dash to safety.
Police stressed there is no specific threat to the shopping centre and the exercise had been planned since last December, but it has given them and businesses the opportunity to test their emergency terror response.
The current UK terror threat level is described as severe, meaning an attack is highly likely, according to the security services.
The exercise, codenamed Exercise Winchester Accord, is the fourth major exercise in months, coming after previous ones in London, Glasgow and Essex.
Greater Manchester Police, the North West Counter Terrorism Unit and the North West Ambulance Service were all being tested as part of the exercise, with no personnel being told precisely how the "attack" would unfold.
The Manchester Evening News understands the SAS was also involved in the operation.
The sound of gunfire could be heard ringing out through the food court as the volunteers screamed for help.
A mock masked gunman appeared at the foot of the steps near the entrance to The Orient, firing a number of shots.
Earlier, the volunteers had gone through a safety briefing and had been reassured that no live rounds would be used.
After observing the initial "attack", members of the press were asked to move outside to witness the arrival of armed police.
Two officers - carrying what appeared to be rifles - moved cautiously towards the entrance, pointing their weapons in front of them.
One covered the other as the pair went inside the food court, ignoring the "injured" as they passed them.
The latest drill took place while the shopping centre was closed to the public between midnight and 6am.
It will continue in locations in the North West, including Red Bank Community Home, a disused young offenders' centre in Newton-le-Willows, Merseyside.