The four will be questioned Friday morning about their roles in demonstrations September 20-21 in Barcelona, when Spanish police arrested several Catalan government officials and raided offices in a crackdown on preparations for an October 1 referendum on independence. Spanish authorities say the demonstrations hindered the police operation.
The four include regional police chief Josep Lluis Trapero and Jordi Sanchez, the head of the Catalan National Assembly that has been the main civic group behind the independence movement.