Over six nights of sometimes-violent protests triggered by a rapper's jailing, Spanish police have arrested at least 160 people.

Most of those arrested were protesting in rapper Pablo Hasel's home region of Catalonia, where major cities like Barcelona have seen six consecutive nights of protests and rioting.

Catalan police said Monday that 129 people in the region had been detained since last Tuesday.

The protests aim to free Hasel, who was sentenced to nine months in prison for glorifying terrorism and insulting the Spanish monarchy and police in his song lyrics and tweets.

Amnesty International has decried the sentence. A group of around 200 Spanish artists, including film director Pedro Almodovar and actor Javier Bardem, signed a petition in his support, warning that Spain's free speech laws pose a threat to "all public personalities who dare to openly criticize the actions of state institutions."

But the protests have gone far beyond peaceful demonstrations in favor of free expression.

 Spain: 160 arrested over 6 nights of violent protests

On several occasions, protestors were seen looting shops and other businesses. On Saturday, rioters shattered the windows of Nike, Tommy Hilfiger, Versace and Diesel stores on the Barcelona shopping street of La Gracia, breaking in and taking whatever they could.

A favorite tactic of the protestors is forming barricades between themselves and police, using anything moveable on the street – large garbage containers, vehicles, street signs, or café tables. They pile them up and set them ablaze, making it more difficult for police to pass but also causing widespread damage.

The flaming barricades have damaged roads and nearby buildings and even melted traffic lights. In Barcelona alone, the damage to public property has been pegged at around $1 million.

The protests have also given way to direct clashes between police and protestors. Protestors often hurl objects at police, while police freely charge crowds with batons and vans.

Several people have been seriously injured, including a young woman who lost her eye after being shot with a rubber bullet.

Outside of Catalonia, protestors have also been arrested in Madrid, Bilbao, Granada, and Pamplona.

More protests have been called for Monday night in Barcelona, set to mark seven straight days of clashes in the Catalan capital.