After spending five months on the run from Spanish authorities, Catalonia’s former president has been detained in Germany by highway police after the separatist crossed the border with Denmark.

Carles Puigdemont’s capture on an international warrant on Sunday, aided by Spanish intelligence services, sparked protests in Catalonia’s main city of Barcelona and other towns in the wealthy northeastern corner of Spain.

Tens of thousands of people joined the rallies, clashing with riot police and leaving more than 50 civilians and police officers injured and leading to four arrests.

Mr Puigdemont will appear before a German judge on Monday.

Spain was plunged into its worst political crisis in four decades when Mr Puigdemont’s government flouted a court ban and held an ad-hoc referendum on independence for the northeastern region in October.

The Catalan parliament’s subsequent declaration of independence received no international recognition and provoked a takeover of the regional government by Spanish authorities that they say won’t be lifted until a new government that respects Spain’s Constitution is in place.

Spain’s state prosecutor office said it was in contact with its German counterparts to carry out its request to extradite Mr Puigdemont to Spain, where he faces charges including rebellion that could put him in prison for up to 30 years. 

Mr Puigdemont was arrested by German police near the Danish border. Photo: Getty

In Barcelona, riot police shoved and struck protesters with batons to keep an angry crowd from advancing on the office of the Spanish government’s representative.

Police vans showed stains of yellow paint reportedly thrown by protesters.

Reinforcements were called in after several hours to clear the neighbouring streets, with protesters tossing street barriers and burning two garbage bins as they retreated.

Outside the city centre, groups of demonstrators cut off traffic on four different stretches of highways.

Police also used batons to keep back a crowd of a few thousand who had gathered in front of the Spanish government’s representative in the city of Lleida.

German highway police stopped Puigdemont on Sunday morning near the A7 highway that leads into Germany from Denmark, police in the northern state of Schleswig-Holstein said.