Protests in support of a jailed Catalan rapper have descended into violence, with police and demonstrators clashing in Spain's main cities.
The protests erupted a day after Pablo Hasél was jailed for tweets insulting police and the Spanish monarchy.
Thousands of protesters in Madrid and Barcelona were met by riot police carrying batons and shields.
Dozens have been arrested, including at least 14 in Madrid and 29 in Barcelona, police said.
In the Spanish capital, a demonstration started peacefully, with protesters clapping their hands and chanting "No more police violence" and "Freedom for Pablo Hasél".
But after bottles and stones were thrown at riot police, they used tear gas and rubber bullets.
The city's conservative mayor, José Luis Martinez-Almeida, condemned the violence, tweeting: "The violent and those who do not accept the rules have no place in our society."
Similar scenes were seen in Barcelona, where protesters set up barricades and set fire to furniture in the streets.
Stones, bottles and blunt objects were thrown, prompting officers to respond by using foam bullets and charging the protesters, police say.
Violent protests were reported in Lleida - the 32-year-old rapper's hometown, and where he was arrested - as well as in the towns of Gerona and Tarragona, police said.
Hasél, whose real name is Pablo Rivadulla Duro, was taken to prison on Tuesday. He had missed a deadline last Friday to give himself up to police and begin serving a jail term handed down in 2018.
Police had stormed a university building where Hasél had barricaded himself and arrested him, triggering rallies and riots in Barcelona and other Catalan cities.
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The rapper faces nine months in prison for glorifying terrorism and slandering the crown in tweets and song lyrics.
The case of Hasél - known for his radical leftist views - has reignited a debate about free speech in Spain.
On Wednesday, Hasél said his arrest had unleashed a wave of outrage against what he described as fascist Spanish institutions.
Spanish rapper Pablo Hasel who barricaded himself inside a university to avoid a jail term has been arrested.
Catalan police entered the University of Lleida and detained him a day after he arrived there with supporters.
Hasel is facing a nine-month jail term for glorifying terrorism and slandering the crown and state institutions over tweets and lyrics that attacked the monarchy and police.
He was due to hand himself in last week but defied the order.
Almost two hours after officers from the Mossos police force went in early on Tuesday, Hasel was led away shouting "they will never silence us; death to the fascist state".
He was driven away to the nearby Ponent prison, where he will begin serving his sentence, reports say.
Dozens of supporters had earlier built a barricade at the university in Lérida (Lleida in Catalan), 150km (90 miles) west of Barcelona. Pictures from the scene showed activists spraying fire extinguishers at police before he was arrested in the university rector's building.
On Tuesday night protests broke out in cities across the country. In Barcelona thousands gathered, waving placards reading "Free Pablo" before the protests turned ugly as police charged and demonstrators set rubbish bins on fire.
Many also chanted calls to free leaders of Catalonia's independence movement, a cause that Hasel supports. Nine were jailed in 2019 after organising an independence referendum for the region two years earlier that the Spanish government called illegal.
A spokesman for the Catalan police force told the AFP news agency that officers had entered the university "to enforce the judicial ruling".
More than 200 artists, including film director Pedro Almodóvar and Hollywood star Javier Bardem, had signed a petition against his jail term, which was upheld by a Spanish court on Monday. Amnesty International tweeted that Hasel's arrest was terrible news for freedom of expression in Spain.
Hasel tweeted overnight that he would go to prison "with my head held high" if he was taken away. "We cannot allow them to dictate what we can say, what we can feel or what we can do," he tweeted, adding that he had chosen not to go into exile abroad.
The Spanish government said last week it planned to reduce the penalty for "crimes of expression" such as the glorification of terrorism, hate speech and insults to the crown and religion, in cases that involve artistic or cultural activities. Besides attacks on the monarchy, Pablo Hasel's tweets and lyrics accused police of torturing and killing demonstrators and migrants.
The singer was found guilty of glorifying terrorism in a separate case in 2014, but his prison sentence was suspended in 2019 on condition that he did not reoffend within three years.
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In one message Pablo Hasel - real name Pablo Rivadulla Duro - expressed support for Victoria Gómez, a jailed member of the banned Marxist group Grapo. Elsewhere he accused King Felipe VI and his father Juan Carlos, the former king, of several crimes.
Spain's freedom of speech controversy
Pablo Hasel will become the highest-profile person to have actually gone to prison for a speech crime in Spain in recent years. But his case is only one of many that have caused controversy.
Several other performers and bloggers have fallen foul of the criminal offence of "glorifying terrorism", which is framed so broadly that any example of justifying a terrorist act, even if it took place a long time ago, can lead to a conviction.
In 2018 the rapper Valtònyc had his jail term confirmed by Spain's Supreme Court, for glorifying terrorism and insulting the monarchy with his promises of bullets for right-wing politicians and a noose for the king.
The year before, Twitter user Cassandra Vera had been sentenced to prison for merely making jokes about the 1973 assassination of Gen Franco's number two, Adm Luis Carrero Blanco, in a bomb attack by Eta Basque militants, although she was acquitted on appeal.
The government has promised to review the law. The legal framing of speech crimes might seem a dry, academic subject, but an explosion of graffiti artwork in Spanish cities in defence of Hasel in recent days suggests that many among Spain's youth believe there is a real issue of freedom at stake.
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