One of those taken into custody was Jordi Turull who was to be the subject of a vote in the Catalan parliament on Saturday for regional president.
Protesters gather near the Spanish government office headquarters after Spain's Supreme Court ruled some Catalan leaders will be tried for rebellion, embezzlement or disobeying the state, in Barcelona, Spain on March 23, 2018.
Announcing the rebellion charges, which carry a maximum sentence of 30 years' imprisonment, Llarena said Catalan separatist politicians and grassroots groups had "colluded" for the past six years to draw up a plan for regional independence in defiance of Spain's legal and constitutional order.
Former Catalan leader Carles Puigdemont faces arrest in Finland after authorities there received an global warrant for his detention issued by Spain, the latest legal action against separatist politicians from the wealthy northeastern region.
Yesterday, worldwide and European arrest warrants were issued for Puigdemont and five of his escorts who also fled the country.
The court also issued worldwide arrest warrants for six other Catalan figures who have fled overseas, including former regional president Carles Puigdemont.
A judge said the five were serious flight risks.
The unity of Spain is enshrined in the Constitution, which says the country is "indivisible", and courts have blocked Catalonia's independence efforts at every turn.
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The decision sparked a wave of demonstrations in Barcelona and across Catalonia on Friday. "Long live a Catalan Republic for all!", she said in a letter published in the Spanish media.
"The [parliamentary] session has been canceled", speaker of the Catalan parliament Roger Torrent said at the session's opening.
Turull earned the votes of his "Together For Catalonia" group and the Republican Left, while the CUP's four members abstained.
He failed to get a majority of votes in the Catalan Parliament because he was not endorsed by the smallest of the three separatist parties that hold a narrow majority of seats in the assembly. Catalans remain divided on whether or not to split from Spain.
The Spanish government called new regional elections in December, in which secessionist parties won again.
Wild protests have erupted in the Basque region of Barcelona after a Spanish High Court detained five Catalan politicians for their role in the region's secessionist bid staged in October previous year.
They include Jordi Turull, a former minister of the ousted regional Cabinet, who on Thursday failed in his bid to be elected as the region's new president.
Turull could still be chosen in a second vote due to take place on Saturday when only a simple majority is needed, but it is unclear whether this will happen.