More armed police will be deployed to the streets of Sheffield following a series of anti-terror raids in the city.
David Hartley, assistant chief constable of South Yorkshire Police, said members of the public can expect to see more officers carrying guns in public places.
He said: "We are working very closely with our colleagues in the North East Counter Terrorism Policing Unit with our shared commitment to find and tackle those that want to cause harm.
"I have further enhanced our armed reassurance to encourage life and business as usual.
"Do say 'hello' to our armed and unarmed officers when you see them."
Meanwhile, the Royal Logistics Bomb Disposal Team arrived outside the Fatima Community Centre in Brunswick Road, Burngreave, at about 5pm which has been cordoned off all day by police.
The squad are understood to have earlier carried out a controlled explosion during a counter terrorism raid in Chesterfield.
The North East Counter Terrorism Policing Unit has raided four properties in Sheffield today - two in Burngreave, one in Stocksbridge and one in Meersbrook. A search warrant was also executed at a property in Chesterfield.
A search of the property in Stocksbridge has concluded while work is continuing at the other sites.
Three men, aged 22, 36 and 41, arrested in Sheffield and a 31-year-old man arrested in Chesterfield remain in custody.
All four were arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism under section 41 of the Terrorism Act 2000.
They have been taken to West Yorkshire for questioning.
A spokesman for the North East Counter Terrorism Policing Unit said the raids were 'intelligence led' and 'pre-planned'.