Thousands of angry protesters took to the streets of Barcelona on Monday after Spain's Supreme Court sentenced nine Catalan separatist leaders to between nine and 13 years in jail for sedition over the failed 2017 independence bid.

As the news broke, demonstrators turned out en masse, blocking streets in Barcelona and elsewhere as police braced for what activists said would be a mass response of civil disobedience.

The long-awaited ruling capped weeks of rising tension, and puts the Catalan question at the heart of the political debate less than a month before Spain heads into its fourth general election in as many years.

Ahead of the ruling, Barcelona had woken up to a heavy police presence, with forces noticeably visible around the regional high court, the main Sants train station and El Prat, Spain's second busiest airport.

“I feel very affected by the sentence even though I expected it. I feel fury and a sense of powerlessness,” said Joan Guich, a 19-year-old maths student who was protesting on Gran Via.

“They have been convicted for an ideology which I agree with.”

The 12 defendants were put on trial in February for their role in the banned October 1, 2017 referendum and the short-lived independence declaration that followed it.

The harshest sentence of 13 years was handed to former Catalan vice president Oriol Junqueras who served as the main defendant in absence of Carles Puigdemont, the region's leader who fled Spain to avoid prosecution.

'An outrage'

In a tweet from Brussels, Puigdemont denounced the sentences as an “outrage”.

“100 years in all. An outrage. Now more than ever, by your side and those of your families. It is time to react as never before,” he wrote.

And in a letter to his supporters released on Monday, Junqueras said the story was far from over.

“Nothing ends today, you neither win nor convince,” he wrote in remarks directed at Spain's central government. “We will come back even stronger... and win."

Spain's government has expressed hope that the trial's end would allow it to move on from the crisis in the wealthy northeastern region, where support for independence had been gaining momentum over the past decade.

“Following the Supreme Court decision we need to turn the page based on peaceful co-existence in Catalonia through dialogue,” Spanish Prime Minister Pedro Sanchez said, speaking in English.

'Democratic tsunami' of protest

But Junqueras' leftwing ERC party has said dialogue would not be possible without an “amnesty” for “political prisoners and those in exile”.

Barcelona Football Club also tweeted its own response to the ruling, saying: “Prison is not the solution.

“The resolution of the conflict in Catalonia must come exclusively from political dialogue.”

The separatist movement is hoping the guilty verdicts will unite their divided ranks and bring supporters onto the streets.

“It is time to rise up against the authoritarian fascism of the Spanish state and its accomplices,” tweeted the radical CDR, whose activists briefly blocked Barcelona's Sants station on Sunday and cut traffic on one of its main streets.

“It is time for the #PopularRevolt.” “Democratic Tsunami”, a newly formed group set up to coordinate the response, called on demonstrators to meet in Barcelona's Plaza Cataluna Monday afternoon, while the Catalan National Assembly (ANC) and Omnium Cultural, the region's two biggest grassroots pro-independence groups, have called an evening rally.

In the coming days, demonstrators will march from five towns towards Barcelona where they will congregate on Friday, when a general strike has been called.

For many, the situation has brought back memories of tensions in the street in the run-up to the October 1, 2017 referendum which was marred by police violence, and ahead of the short-lived independence declaration that followed on October 27.

Former parliamentary speaker Carme Forcadell was handed 11 years and six months in prison, while five other former ministers were jailed for between 10 years and six months and 12 years.

Two influential Catalan civic leaders, Jordi Sanchez and Jordi Cuixart, were sentenced to nine years in prison, while the remaining three leaders escaped jail time and were each handed a fine of around 60,000 euros ($70,000).

Sedition is “rising up publicly and in turbulent fashion” to “prevent by force or in an illegal way” the law from being applied, or the application of an administrative or legal decision.