Thousands of protesters have taken to the streets to protest at the jailing of nine former members of the regional government following an appearance at Spain's National Court for questioning in a probe over Catalonia's push for independence.

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 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.

The seven men and two women were taken from the Madrid court following the ruling in police vans with sirens wailing.

Investigative Magistrate Carmen Lamela's ruling granted the request of prosecutors after the nine were questioned at the National Court in Madrid.

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.

Carles Puigdemont, the former president of Catalonia, and four other ex-Cabinet members are in Belgium and ignored court summonses to appear for questioning.

Lawyers for the nine ordered jailed said the defendants are serene and want 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.