(CNN) Protests broke out in Barcelona Sunday after news that Catalonia's former separatist leader Carles Puigdemont had been detained in Germany.

The ex-president of Spain's northern Catalonia region is being held at a police station in Germany, according to a tweet from his lawyer, Jaume Alonso-Cuevillas.

Puigdemont was en route to Belgium from Finland and was detained after crossing the border from Denmark. German police said in a statement that Puigdemont was arrested in the northernmost state of Schleswig-Holstein.

Protesters scuffle with riot police at a demonstration in Barcelona on March 25, 2018.

Puigdemont has lived in self-imposed exile in Belgium since October, after spearheading Catalonia's referendum on whether to secede from Spain.

The independence drive plunged the country into its worst political crisis in decades, with Madrid denouncing the referendum as illegal and calling for Puigdemont's arrest.

A protester is pulled by riot police blocking the road leading to the central government in Barcelona on March 25, 2018.