Protests broke out across the Spanish region of Catalonia on Sunday after former leader Carles Puigdemont was taken into custody in Germany.
At least 89 people were injured in clashes with police and four arrests were made.
Mr Puigdemont, who is wanted in Spain for sedition and rebellion, was detained by German police acting on a European arrest warrant.
He will appear before a German judge later on Monday.
Mr Puigdemont was detained while crossing from Denmark on his way to Belgium, where he has been living in self-imposed exile since Catalonia’s parliament unilaterally declared independence from Spain in October.
Germany has 60 days to decide whether to return him.
In order to do so, its judges need to assess whether the Spanish charges are punishable under German law.
Criminal lawyer Martin Heger told Germany’s Spiegel website (in German) that the lesser charge of misappropriation of public funds was also a crime under German law, and therefore it was clear that the exiled ex-leader would have to be extradited.
However, if he is extradited on that charge, he can only be tried on that offence.
It is unclear whether the alleged crimes of rebellion and sedition are punishable in Germany.
The extradition procedure can last about two months.
Mt Puigdemont also has the right to oppose the warrant and apply for asylum in Germany.
Spain’s latest move is considered the most serious challenge to date to the Catalan independence movement. Almost the entire leadership now faces a major legal fight.
Various other Catalan politicians have been subjected to new warrants, including Catalonia’s former education minister, Clara Ponsati. She is in Scotland, where she has a position at the University of St Andrews, and is preparing to hand herself in.
The number of European arrest warrants issued has increased since 2005, according to EU figures. In 2015, about 16,000 warrants were issued and about 5,000 executed.
How did we get here?
1 October 2017: The independence referendum takes place in Catalonia; it is deemed illegal by Spain and boycotted by many potential voters
27 October: Catalonia’s leaders declare independence, which leads to the Spanish government imposing direct rule on the region and dissolving its parliament
30 October: Charges of rebellion, sedition and misuse of public funds are brought against various sacked members of the Catalan government, including Mr Puigdemont
2 November: Several former Catalan ministers are taken into custody in Spain
3 November: European arrest warrants are issued against Mr Puigdemont and four of his allies, who have all fled to Belgium
5 December: A Spanish judge withdraws the European arrest warrants but says the group still face possible charges for sedition and rebellion
21 December: Carles Puigdemont is re-elected to parliament during Catalan’s regional elections – which Spanish PM Mariano Rajoy had called to “restore democracy”
1 March 2018: Mr Puigdemont says he is stepping aside and he backs detained activist Jordi Sanchez to run as Catalonia’s president
21 March: Mr Sanchez drops his leadership bid and instead the candidacy is passed to Jordi Turull, who the following day is rejected by hardline separatists
23 March: Mr Turull and various others are arrested in Spain, and the European arrest warrants are reissued
25 March: Mr Puigdemont is detained in Germany