Four men have been arrested in raids in Yorkshire, Derbyshire and the West Midlands, on suspicion of plotting acts of terrorism
Three, in their 30s, were detained from addresses in Leeds, Huddersfield, and Derby, while a fourth, a 49-year-old, was arrested in West Bromwich.
They were detained on suspicion of the commission, preparation or instigation of acts of terrorism under Section 41 of the Terrorism Act 2000, police said.
They have all been taken to a local police station for questioning.
Searches are ongoing at a number of properties.
A spokeswoman for Counter-Terrorism Policing North East said: “This activity was pre-planned and intelligence-led and there is not believed to be any imminent threat to the public in the UK linked to this investigation.”
She said all four of those detained were British nationals.