As debates over free speech and accusations of “cancel culture” continue to simmer across the world, the issue last week emerged as a fierce rallying cry on the streets of Spain.

A provocative Spanish rapper became an unlikely figurehead for widespread protests and galvanized a debate about freedom of expression in the European country.

Pablo Hasél’s tweets and lyrics came back to haunt him, as the anti-establishment musician was imprisoned last Tuesday on charges of insulting Spain’s monarchy and glorifying terrorism, sparking night upon night of protests in major cities across the country, some of which have turned violent.

Hasél — whose full name is Pablo Rivadulla Duró — missed a deadline earlier this month to surrender to police to serve a nine-month jail term handed down in 2018, when he was convicted over lyrics and tweets that compared Spanish judges to Nazis and called former King Juan Carlos a mafia boss. He also made references to the Basque separatist paramilitary group known as ETA, which sought independence from Spain.

Instead, Hasél barricaded himself in a university in the Catalan city of Lleida before he was eventually arrested and jailed.

“Tomorrow it could be you,” he tweeted before he was imprisoned and after retweeting the lyrics that he was convicted for.

“We cannot allow them to dictate to us what to say, what to feel and what to do,” he added.

His supporters and those who decry the perceived limits on free speech took to the streets of cities including the capital, Madrid; Valencia; and Catalonia’s regional capital, Barcelona, where thousands chanted, “Freedom for Pablo Hasél,” and, “No more police violence.”

As tensions flared Saturday, police clashed with members of fringe groups who set up street barricades and smashed storefront windows in downtown Barcelona.

Pepe Ivorra García, 18, a student in the city who joined the protests Thursday night, said he came out to peacefully support Hasél and what he called an “attack” on democratic freedoms that are “part of the backbone” of the Spanish Constitution.

“I’m neither Catalan, nor pro-independence but I am a democrat,” García told NBC News. “I humbly consider it to be an embarrassment and a democratic anomaly that in a European country in the 21st century there are prisoners in jail for their ideas.”

Hasél became an unlikely free speech champion after his case drew attention to Spain’s 2015 Public Security Law. Enacted by a previous, conservative-led government, the law prevents insults toward religion, the monarchy and the glorification of banned armed groups such as ETA.

More than 200 artists, including film director Pedro Almodóvar and actor Javier Bardem, signed an open letter last week in solidarity with Hasél.

Human rights organization Amnesty International Spain also condemned the rapper’s imprisonment as a “disproportionate restriction on his freedom of expression.”

The so-called 2015 “gag law” has been a “step backwards” for freedom of expression and peaceful assembly in Spain, said Koldo Casla, a law lecturer at England’s University of Essex and former chief of staff of the human rights commissioner of the Basque Country.

“Public authorities were given excessive leeway to impose administrative fines, with chilling effects on peaceful demonstrations,” he told NBC News.

Casla said although Hasél’s songs could be deemed “cruel or deplorable” they were not sufficient reason to apply the criminal code. He added that the furor created by his case should be an opportunity for lawmakers “to amend the criminal code to make sure it is compatible with the highest standards of freedom of expression.”

The debate has prompted Spain’s ruling leftist coalition government to announce it will seek to reform the 2015 law by introducing milder penalties and giving greater tolerance to artistic and cultural forms of expression.

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The Spanish protests, however, should worry neighboring countries, Patrick Breyer, a member of the European Parliament, told NBC News. He said Hasél’s case represented an attack on “legitimate dissent” and should be of “great concern” to the European Union.

“Spain is going way too far, interpreting and using its anti-terror laws, and I’m afraid it might spill over,” Breyer said. “I think satire, jokes and arts are a very important part of society … and that it’s counterproductive to crack down on this kind of speech, and the same applies to criticism of the police and crown — that’s extremely important in a democracy.”

Spanish Prime Minister Pedro Sánchez condemned violence at the protests.

“Democracy protects freedom of speech, including the expression of the most awful, absurd thoughts, but democracy never, ever protects violence,” he said on Friday.

Not all Spaniards are supportive of Hasél’s case.

Rafa Morata, 49, a primary school teacher, dismissed the rapper as a “leftist extremist,” telling NBC News his arrest was not about his lyrics or tweets but because he had been “glorifying terrorism.”

“His entry into prison has led to a debate about freedom of expression that his supporters have used to provoke riots in the streets,” Morata said, adding that the law had unwittingly turned Hasél “into a victim and a hero.”

The Associated Press and Reuters contributed to this report.

Matthew Mulligan contributed.