The move is part of the wider Operation Temperer to address safety and provide reassurance to the public and comes in response to the UK terror threat level being raised to ‘critical’.
Armed officers have been out patrolling a number of public areas today including at Sheffield and Doncaster railway stations, plus Doncaster Sheffield Airport, and this is set to continue over the weekend.
Additional armed officers, drawn from the Civil Nuclear Constabulary, are being deployed in support of firearms officers in South Yorkshire.
South Yorkshire firefighters will also be out and about in public areas.
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."
Steve Gill, chief executive of Doncaster Sheffield Airport, said: “We can confirm that additional security checks are now in place at all UK airports. UK Border Force are now conducting additional passport checks before the security channel.
“These additional checks are for the safety and security of our passengers, which remains our number one priority.”
Stringent new security measures will be in place at Bramall Lane for the IBF World Welterweight title fight between Kell Brook and Errol Spence Junior on Saturday night.
Full-body searches will take place upon entry to the venue and no bags will be allowed into the stadium for the fight.
Dog units will also be in operation and fans are urged to allow extra time to get into the venue.
Meanwhile, Sheffield's Northern General Hospital and Children's Hospital are among 27 hospitals that have been put on alert to standby to deal with a possible terror attack this weekend.
In a message sent out to hospitals, Chris Moran, NHS England’s national clinical director for trauma, said: "The trauma community in Manchester has provided a tremendous response to the atrocity on Monday night and this is a credit to their dedication and clinical skills, and also the preparation that has taken place. You will be aware that we have a bank holiday weekend approaching.
"There are a number of things that all trauma units and major trauma centres can do to prepare for a further incident and I should be grateful if you could disseminate these within your network so that frontline clinicians are aware.”
A spokesman for NHS England said: "Since the [Joint Terrorism Analysis Centre] has announced the threat level has changed from severe to critical, this triggers longstanding, tried and tested NHS protocols reflected in this letter, which reminds NHS organisations of the precautionary measures they need to take ensure care is in place should it be needed.”
As part of Operation Temperer up to 5000 troops are thought to have been deployed to the streets of the UK to provide extra security and reassurance at key locations. The Home Office and South Yorkshire Police are yet to confirm if military personnel will be on our streets.
The terror attack at the Manchester Arena on Monday night left 22 people dead, including Sheffield woman Kelly Brewster, and dozens injured.
The Islamic State terror group claimed responsibility for the barbaric attack, in which suicide bomber Salman Abedi detonated an explosive device as fans were leaving an Ariana Grande pop concert.