Shoppers were part of a practice evacuation at the Grosvenor Shopping Centre in Chester.
Security in the city centre has been stepped up in the wake of the Manchester terror attack.
Cheshire police said there was 'nothing to be worried about' during the test at about 9.30am on Tuesday (May 30).
From the Chester LPU account, the force tweeted that officers were on the scene to reassure the public.
Armed officers have been a visible presence in the city centre in the week since the horrendous bombing of Manchester Arena.
An address in Chester, which has not been revealed, was raided in connection with the investigation into the attack early on Monday.
There is no specific intelligence to indicate Chester is being targeted by the terrorists.
The UK terror threat level has been reduced from critical to severe, but the increased patrols are continuing for now.
Detective Superintendent Aaron Duggan said: "Officers will be visible in Chester over the next few days providing reassurance and if any members of the community have any concerns then I would encourage you to speak to local officers.
“We will continue to work closely with our communities by carrying out patrols over the coming weeks and addressing any concerns they may have."