Armed police have flooded a neighbourhood in Sheffield in what one witness said appeared to be a counter terrorism operation.
One witness said counter terrorism police appeared to be raiding a flat in Kelham Island this afternoon, at around 5.30pm.
Another witness, Tom Greasley, told how he had seen around 100 officers - about half of whom were armed with machine guns - near the Shalesmoor tram stop.
"There are fire engines, two bomb disposal squads, ambulances and endless amounts of coppers with machine guns," he said.
"I saw at least 15 police cars driving through. I'd say there are at least 100 police officers dotted about, around half of whom must be armed."
Police cordoned off Dun Street and Cornish Street.
A spokesman from the North East Counter Terrorism Unit said: "Officers have today arrested two men from Huddersfield on suspicion of offences under Section 5 of the Terrorism Act.
"The men, age 24 and 29, were arrested at separate locations in Huddersfield and Sheffield.
"Searches are being carried out in properties in Huddersfield and Sheffield.
"There are no connections to the recent incident and investigation in Manchester.
"The operation is based on recently received intelligence.
"We understand that people may have concerns as a result of this activity and we are grateful for the patience and understanding of the public while these enquiries are carried out.
"The public may have heard loud bangs at the time that police entered the property. We would like to reassurance you that this was part of the method of entry to gain access to the property."