15 of the 20 former Catalan leaders accused of rebellion, sedition and misuse of public funds—including the former Deputy First Minister, Oriol Junqueras (Esquerra, ERC)—showed up at the National High Court or Supreme Court in Madrid on Thursday morning, as ordered by the judges.

The first person to answer the court's questions, at the first pre-trial hearing of the investigation, was Jordi Turull, the former Catalan government spokesman.

Five others—Carles Puigdemont and four of his former regional ministers: Clara Ponsatí (education), Toni Comín (health), Lluís Puig (culture) and Meritxell Serret (agriculture)—are still in Brussels, where they fled on Monday.

La Vanguardia, citing "sources close to the dismissed executive", confirmed the five were still in the Belgian capital and not about to turn up to court late.

Several Spanish media outlets reported the Public Prosecutor's Office was preparing to ask for a European Arrest Warrant for Mr. Puigdemont and the four others who had not appeared on Thursday morning.

A statement issued on Wednesday evening by the "legitimate government of Catalonia" announced the five would "denounce this political trial" from abroad and described "disproportionate" maximum sentences.

The crime of rebellion could lead to up to 30 years in jail for leaders of the plot, according to the 1995 Spanish Criminal Code.

Shortly before 11 a.m., it was reported the Supreme Court had decided to delay questioning the Speaker of the Catalan Parliament, Carmen Forcadell, and five of the former members of her Speaker's committee by one week, until November 9, after a request by lawyers.

On Wednesday evening, those former ministers who travelled to Madrid on the AVE high-speed train were greeted at Atocha station by an angry group of onlookers waving Spanish flags and had to be protected by National Police officers.

One far-right group, Hogar Social Madrid, posted a video on its Facebook page of its members taking part in the demonstration.

Several well-known Catalan and left-wing politicians turned up outside the court building to support the accused.

Esquerra MP Joan Tardà said: "This is a sad day for me, it hurts me that in 2017 in the middle of the European Union we have to watch this".

Former First Minister Artur Mas spoke to reporters: "The conflict between Catalonia and Spain is not going to be solved with courts and violence".

Popular Party spokesman Fernando Martínez-Maillo said during a TV interview on Thursday morning that Mr. Puigdemont's continued presence in Brussels was "absolutely grotesque".