Ousted Catalan leader Carles Puigdemont has described the imprisonment of several of his former Cabinet members in a probe over the region's push for independence as "a serious mistake".
In a speech broadcast late last night by Catalan public TV3, Mr Puigdemont called on Catalans to protest against the Spanish authorities "without violence, peacefully and with respect for everybody's opinions".
Mr Puigdemont and several ousted Cabinet members remain in Brussels, where he said they are seeking "safety and freedom" while judges back in Spain investigate them for pushing Catalan secession.
The prosecutor has asked the National Court judge to issue an international arrest warrant against them.
"The fury with which the Spanish government has attacked a beautiful European nation is outrageous and is threatening us all," Mr Puigdemont said, adding that Catalonia's independence is "no longer an internal affair" of Spain.
The ousted leader reacted to the events at Spain's National Court in Madrid as thousands of protesters took to the streets to protest at the jailings.
Eight of the nine were jailed without possibility of bail while they are investigated on possible charges of sedition, rebellion and embezzlement following the regional parliament's declaration of secession from Spain last week. Bail of 50,000 euros (£44,000) was set for the ninth.
Protests were called for Thursday evening, and thousands gathered in Catalan towns including Tarragona, Lleida, Girona and Barcelona.
The jailed politicians called for all protests to be peaceful and for their supporters to avoid any show of violence. Mass protests in favour of independence in Catalonia have so far been peaceful.
Under Spain's legal system, investigating judges can order the detention of suspects while a comprehensive probe, sometimes taking months, determines if charges should be brought.
Lawyers said the defendants were serene and wanted the people of Catalonia to stay calm.
Defence lawyer Jaume Alonso-Cuevillas said the decision "lacked justification" and was "disproportionate".
He is representing former regional vice president Oriol Junqueras and four other ousted members of the Catalan Cabinet.
Van den Andreu, the lawyer defending other ex-members of the regional government, said whether his clients were jailed "was already predetermined" before they appeared in court.
Both lawyers said they would appeal the judge's order.
Mr Puigdemont reacted on Twitter to the jailing of nine members of his former Cabinet, posting that "the legitimate government of Catalonia has been jailed for its ideas".
He tweeted the government's "furious clamour" had sent the officials to jail.
"The serene clamour of the Catalans is of freedom," he wrote, posting a photo of protesters in Barcelona.