Madrid's court summoned 13 officials as well as former Catalan leader Carles Puigdemont, who has already said he will ignore the order.
"This is a political trial," said Mr Puigdemont, who is now in Belgium.
Prosecutors could order the officials' arrest if they fail to appear in court.
Spain has been gripped by a constitutional crisis since the referendum was held on 1 October in defiance of a constitutional court ruling that had declared it illegal.
Last week, Spanish Prime Minister Mariano Rajoy imposed direct rule on Catalonia, dissolving the regional parliament and calling snap local elections.
The Catalan government said that of the 43% of potential voters who took part in the referendum, 90% were in favour of independence.
Catalonia crisis in 300 words
What next for Spain?
Puigdemont: The man who wants to break up Spain
What is expected in the Madrid court?
They were ordered to appear in Madrid's Audiencia National (high court) on Thursday morning for questioning.
They are yet to be formally charged.
A judge will have to decide whether the officials should go to jail pending an investigation that could potentially lead to a trial.
The judge can also grant them conditional bail and order them to surrender their passports.
It is unclear how many of those summoned will actually appear in court.
However, Mr Puigdemont earlier made it clear he would not be coming to Madrid.
"Those summonses are part of proceedings that lack any legal basis and only seek to punish ideas. This is a political trial," he said in a statement.
Mr Puigdemont previously said he would return to Spain if he and his colleagues received guarantees of a fair trial.
The Spanish government insists it has no influence over the country's judiciary.
But if those Catalan politicians appearing in court are denied bail it will cause further anger among those who want Catalonia to break away, our correspondent adds.
The court summons also gave them three days to pay a deposit of €6.2m ($7.2m) to cover potential liabilities.
No comments: