Two men have been arrested on suspicion of terrorism offences.
A 36-year-old from Birmingham and 35-year-old from Doncaster are being held on suspicion of conspiracy to distribute terrorist publications.
West Midlands Police said the men were being questioned by the West Midlands Counter Terrorism Unit at a police station in the region.
Searches of addresses in both Birmingham and Doncaster are continuing, said police.
The force said the planned, intelligence-led arrests were made by the counter terrorism unit, with support from South Yorkshire Police.