Catalonia’s ex-leader Carles Puigdemont has been detained by German police acting on a European arrest warrant.
Mr Puigdemont, who is wanted in Spain for sedition and rebellion, was held crossing from Denmark on the way to Belgium, his lawyer said.
Mr Puigdemont will appear before a German judge on Monday.
The ex-leader’s supporters gathered in Barcelona to protest against his arrest. The charges he faces in Spain could result in 30 years in prison.
Mr Puigdemont has been living in self-imposed exile in Belgium since Catalonia’s parliament unilaterally declared independence from Spain in October.
He was visiting Finland last week when the arrest warrant against him was reissued.
He evaded Finnish authorities by slipping out of the country on Friday before they could arrest him.
His court appearance on Monday will be a formality to confirm his identity.
- The man who wants to break up Spain
- Catalan crisis in 300 words
“The president was going to Belgium to put himself, as always, at the disposal of Belgian justice,” his spokesman Joan Maria Pique said.
German police said that Mr Puigdemont was detained by a highway patrol in the northern state of Schleswig-Holstein, which borders Denmark.
After the news of his arrest broke on Sunday, thousands of demonstrators poured on to the streets of Barcelona.
They chanted “Freedom for the political prisoners” and “This Europe is shameful!” as they headed to the offices of the European Commission.
A smaller protest was held in Girona, where Mr Puigdemont once served as mayor.
Tensions in Catalonia are very high and its separatist leaders abandoned plans to name a new president following the arrest of the latest candidate, Jordi Turull, on Friday.
Protesters clashed with police in Barcelona on Friday night after Spain’s Supreme Court ruled 25 Catalan leaders should be tried for rebellion, embezzlement or disobeying the state. Mr Turull was among five people taken into custody in fresh arrests.
The rulings were considered the most serious challenge to date to the Catalan independence movement. Almost the entire leadership now faces a major legal fight.
Following the referendum, the central government in Madrid sacked the Catalan regional government, imposed direct rule and called new elections but pro-independence parties returned with a slim majority.
International warrants for Mr Puigdemont and other Catalan leaders were withdrawn in December by a Spanish judge, who said they had shown a willingness to return to the country.
The warrants were reissued on Friday, surprising Mr Puigdemont, who had been in Finland to give a university lecture.
Among those also wanted is Catalonia’s former education minister, Clara Ponsati. She is in Scotland, where she has a position at the University of St Andrews, and says she is willing to hand herself in.
Who is Carles Puigdemont?
Carles Puigdemont, 55, is a former journalist who worked for pro-independence media in Catalonia and headed the Catalan News Agency.
After moving to politics, he became an MP and later mayor of Girona, north-east of Barcelona.
In 2016, he became leader of Catalonia and led the region to the referendum the following year.
During his self-imposed exile following the resulting crisis, Mr Puigdemont told Belgian TV he was not hiding from “real justice” but from the “clearly politicised” Spanish legal system.