Protesters in Madrid and Barcelona clashed with the police on Wednesday over the arrest of Pablo Hasél, a popular rapper who had barricaded himself in a university to evade a prison sentence for violating Spanish laws restricting speech.
Mr. Hasél was arrested on Tuesday in Lleida, a city west of Barcelona, after he failed to begin serving a nine-month prison term. He had been sentenced two years earlier on charges of glorifying terrorism and insulting the monarchy.
The case has galvanized wide public support in Spain for Mr. Hasél and prompted the left-wing coalition government to say that it plans to overhaul parts of the criminal code.
Protests over Mr. Hasél’s arrest began on Tuesday in Barcelona and other cities in Catalonia in northeastern Spain, where supporters of a regional independence movement have often clashed with the police. Thousands of people took to the streets to demand his release.
The demonstrations continued on Wednesday and expanded to Madrid, Spain’s capital, and other cities. Protesters were seen throwing objects at the police, smashing windows and setting garbage bins on fire, The Associated Press reported.
Journalists at the scene posted images and videos on social media showing large crowds of supporters, many of them wearing surgical masks, chanting about the rapper and squaring off against groups of police officers in riot gear.
“Pablo, comrade, you are not alone,” one crowd chanted on Wednesday in Lleida, the Catalan city where Mr. Hasél was arrested.
The authorities in Madrid said on Wednesday that access to a central train station had been restricted as a result of disturbances to “public order.”
Early news reports indicated that dozens of protesters had been arrested or injured in run-ins with the police. A Reuters journalist in Barcelona was among those injured when officers fired rubber bullets into a crowd, the news agency reported.
Mr. Hasél, whose real name is Pablo Rivadulla Duró, was a popular gadfly well before he was sentenced to prison in 2018.
He has accused the Spanish police of brutality, compared judges to Nazis and expressed support for ETA, a Basque separatist group that dissolved two years ago after waging one of modern Europe’s longest terrorism campaigns.
In 2018, Spain’s High Court sentenced Mr. Hasél to just over two years in prison for glorifying terrorism and insulting the monarchy. The charges focused on his incendiary tweets and a song he had written about King Juan Carlos, who abdicated in 2014. A judge later reduced the sentence to nine months.
Last month, Mr. Hasél was ordered to report to prison by mid-Feburary. More than 200 artists later signed a petition demanding his release.
The public pressure led the Justice Ministry to say on Monday that it planned to change the country’s criminal code to reduce sentences related to the kinds of speech violations for which Mr. Hasél had been sentenced. The ministry did not provide specifics about its plan.
On Tuesday, Mr. Hasél was arrested after he and his supporters barricaded themselves inside a building at Lleida University.
“They will never silence us!” he yelled to reporters as the police led him to a patrol car, the newspaper El País reported. “Death to the fascist state!”
In his last Twitter message before he was incarcerated, Mr. Hasél issued a warning to his supporters.
“Tomorrow it can be you,” he wrote.
His supporters include some Spanish politicians, the director Pedro Almodóvar and the movie star Javier Bardem. Amnesty International called his arrest “an excessive and disproportionate restriction on his freedom of expression.”
“No one should face criminal prosecution only for expressing themselves on social media or for singing something that may be distasteful or shocking,” Esteban Beltrán, the director of Amnesty International Spain, said in a statement hours before Mr. Hasél’s arrest. “Expressions that do not clearly and directly incite violence cannot be criminalized.”
But the rapper’s legal troubles could continue for some time.
Mr. Hasél’s nine-month term may be lengthened to more than two years because he has refused to pay fines associated with his sentence, El País reported. The police are also investigating him for allegedly trying to break into a government building in Lleida during a protest two years ago over the detention in Germany of Carles Puigdemont, the former leader of Catalonia.
