A fifth man has been arrested over an alleged terror attack plot, police said.
Two buildings in Sheffield are being searched by counter-terrorist officers after the 21-year-old from the city was held late on Friday.
It follows the arrests of four men in the South Yorkshire city and nearby Chesterfield in Derbyshire on December 19.
A spokesman for Counter Terrorism Policing North East (CTPNE) said: “The 21-year-old man, from the Fir Vale area of Sheffield, was arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism under Section 41 of the Terrorism Act 2000.
“The intelligence-led arrest was made in the Firth Park area of Sheffield at approximately 11pm on Friday evening.
“Two addresses, a residential address in Fir Vale and a business address in Firth Park, are currently being searched by officers.”
Two of the men arrested on December 19 - Chesterfield fish and chip shop owner Andy Star, 31, and Farhad Salah, 22, from Sheffield - have been charged with one count of engaging in the preparation of an act of terrorism.
The men, both Kurdish Iraqis, are due to appear at the Old Bailey in London on January 19.
A 36-year-old man from Burngreave in Sheffield also remains in custody, while a 41-year-old from Meersbrook in Sheffield was released on Saturday, police said.