South Yorkshire will see an 'increased policing and security presence' in response to the London tube attack.
The threat level across the UK has been raised to 'critical' meaning an attack is 'expected imminently'.
A make-shift bomb went off on a commuter tube as it pulled into Parson's Green station in London on Friday morning.
South Yorkshire Police chiefs are set to ramp up visible patrols at 'key sites' and 'crowded public places to reassure the public.
A South Yorkshire Police spokesman said: "This is what our officers train for and the police service, alongside our partners, will do everything we can to protect you, our public.
"We urge the public to remain vigilant and to report any suspicious activity to the police by calling the confidential anti-Terrorist Hotline on 0800 789321 or in an emergency by dialling 999.
"For further information about reporting suspicious behaviour visit gov.uk/ACT If you get caught up in the rare event of a weapons or firearms attack, we urge you to follow our Run Hide Tell advice."