Spanish intelligence had been keeping an eye on the ex-Catalan President Carles Puigdemont on his way from Finland to Germany, Focus magazine, which, according to Wikileaks' founder Julian Assange, has close ties to German intelligence, reported.
According to the media source, the Spaniards then informed Germany's BKA, the federal investigative police agency that ordered the politician's arrest.
Earlier, it was reported that former Catalan President Carles Puigdemont had been detained in Germany, as he crossed the border from Denmark, on his way to Belgium from Finland, the politician's lawyer Jaume Alonso Cuevillas posted on Twitter.
Carles Puigdemont, who is currently being held at a police station, said that he was ready for talks with the Spanish central government, and believed that his return would be evidence of the normalization of politics and democracy in the country.
READ MORE: Former Catalan President Puigdemont Detained in Germany
On October 1, 2017, Catalonia held a referendum on the region's independence from Spain. The vast majority of voters backed secession. The plebiscite was not, however, recognized by Madrid, which subsequently imposed direct rule over the autonomous region and dismissed its government.
Spanish authorities have opened a criminal case against 30 Catalan politicians and officials, arresting four of them, while Puigdemont, as well as several advisers of the dissolved Catalan government, fled Spain before the trial.