Spanish police arrested some 50 people overnight following a second night of clashes over the jailing of a rapper for a string of tweets insulting police and the monarchy, AFP reports. 

Angry demonstrations first erupted on Tuesday night in Catalonia after police detained Pablo Hasel, 32, who was holed up in a university in that region to avoid going to jail in a controversial free speech case.

And the protests swelled on Wednesday with hundreds gathering under a heavy police presence in Madrid's Puerta del Sol square and calling for his release, later hurling bottles at police, who charged at them in clashes lasting several hours, AFP journalists said.

Police said at least 15 people were arrested, but were due to issue an update on Thursday morning, while the city's emergency services said 55 people were injured, among them 35 police officers.

In Barcelona, demonstrators lobbed objects at police and set barricades ablaze, with police firing foam rounds and charging at the protesters.

Across Catalonia, the Mossos d'Esquadra regional police said 31 people were arrested, including 10 in Barcelona, 14 in Lerida, where Hasel was arrested, five in the northern city of Girona and 2 in Tarragona.

Medics said eight people were slightly injured.

At least 15 people had been arrested on Tuesday night in protests in several Catalan cities in which more than 30 people were injured, among them 19 police officers, officials said.

News.Az