Counter-terrorism police in Leeds have arrested a man on suspicion of the commission, preparation and instigation of terrorist acts.
The 33-year-old was arrested on Saturday and is being held as part of a pre-planned operation into suspected extreme right-wing activity, West Yorkshire Police said.
The force added that a property in Leeds was being searched by officers.
Supt Chris Bowen said public safety was their "top priority".
He added: "If you see or hear something that could be terrorist related, act on your instincts by reporting your concerns."