Puigdemont, who has been living in self-imposed exile in Brussels since October, was travelling in a car on his way from Finland to Belgium on Sunday when he was detained, having visited Finnish lawmakers in Helsinki.

On Friday the Spanish government reactivated an international arrest warrant for Puigdemont and four others, among them a former speaker of the Catalan parliament. Puigdemont is wanted on charges of rebellion, misuse of public funds, and sedition arising from his role in organizing an October referendum on Catalan independence. If convicted, he could face as much as 30 years in prison.

Puigdemont and his separatist allies signed a declaration of independence last October, despite objections by the central government. Madrid responded by dissolving the Catalan parliament and scheduling new elections.