Nine other Catalan leaders have been jailed for their role in an independence push.
A Spanish judge has issued a European arrest warrant for ousted Catalan President Carles Puigdemont.
Spanish Prime Minister, Mariano Rajoy, has maintained that the recent independence referendum was illegal.
The Spanish government last week took back control over the autonomous region.
Eight of their former Catalan regional government colleagues have already been imprisoned without bail while the investigation continues. Former Business Minister Santi Vila, who stepped down from the cabinet before the independence declaration, was granted bail of 50,000 euros ($58,300).
Spanish government spokesman Inigo Mendez de Vigo has said that any politician can stand in the election unless he or she has been convicted of a crime.
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If an arrest warrant against Puigdemont is announced Friday, he could be detained by Belgian police and subsequently face extradition to Spain. Spanish Prime Minister Mariano Rajoy sacked Puigdemont and dismissed Catalonia's parliament, calling a regional election for December 21.
Since then, eight politicians and two activists have been jailed pending trial, and arrest warrants have been issued for five others, including Puigdemont, who fled to Belgium to try to run a government in exile.
His lawyer in Belgium has said that Puigdemont will fight any extradition charges against him.
The Brussels prosecutor's office confirmed that the region's former president and his sacked ministers surrendered after Spain issued a warrant for their arrest.
He said that wanted to appear before the judges but that did not mean a Spanish court.
Hundreds of pro-secession Catalans gathered in town squares across the region Sunday to put up posters in support of independence and to demand the release of the jailed separatists.
DW reporter Charlotte Chelsom-Pill, who was at the scene, said demonstrators chanted "We are not afraid" as they waited for the return of the six Catalan officials who appeared in the Supreme Court. The declaration is deemed mostly symbolic because it is unlikely Spain or the global community will recognize an independent Catalonia.