Additional armed officers, drawn from the Civil Nuclear Constabulary, are being deployed in support of firearms officers in South Yorkshire.
South Yorkshire Police has called upon the resource in line with national procedure under Operation Temperer, which provides additional protective security.
The move is part of an operation to address safety and provide reassurance to the public and comes in response to the UK terror threat level being raised to ‘critical’.
Assistant Chief Constable David Hartley, strategic commander for the force over the bank holiday weekend, said: “Armed colleagues from the Civil Nuclear Constabulary are working alongside our officers at key sites across South Yorkshire, to provide an additional presence and help keep our communities safe.
“Contrary to reports made by some media outlets yesterday, the military are backfilling at high security sites across the UK, in order to free up armed officers, including those who have been deployed to South Yorkshire.
“Our colleagues from the CNC are trained to the same high standards as armed officers at South Yorkshire Police and wear a very similar uniform to our own, making it unlikely that the public will be able to differentiate between SYP staff and the additional support.
“A dedicated, specialised SYP operational team has been running twenty-four hours per day since critical status was declared on Tuesday evening, ensuring armed and unarmed officers are visible in crowded places and planning for future events.
He thanked the public for its support of officers.
“The response from the public on the streets and through social media has been largely very positive. Your messages of support have been shared with our officers and we thank you for your support. It’s very uplifting.
"We will continue to offer support to our colleagues at Greater Manchester Police and wish to extend our sincere condolences to the victims of Monday night’s tragedy, their families and friends.
"Please remain vigilant and alert but not alarmed. If you see anything suspicious report it to the anti-terrorist hotline in confidence on 0800 789321. In an emergency, always dial 999."
The CNC officers will operate under the command and control of South Yorkshire Police.