BARCELONA, Spain (AP) — Several hundred protesters marched Saturday in Spain’s northeastern city of Barcelona against the authorities’ crackdown following a violent outcry over the imprisonment of Pablo Hasél, an anti-establishment artist.

Saturday’s march took place amid a heavy police presence, winding through several avenues of the Catalan regional capital. Protesters walked behind a banner that called for the release of Hasél and his jailed supporters.

The rapper is serving nine months for inciting terrorism — he has praised two now-defunct armed groups responsible for killing over 900 people in Spain — and for refusing to pay a fine for insulting Spain’s former king.

His arrest on Feb. 16 triggered a mix of peaceful and violent protests that have at times ended in the looting of shops in several cities. The case has also invigorated a debate over the limits of freedom of speech in Spain.

Spain’s ruling left-wing coalition has pledged to launch a legal reform to eliminate prison terms for offenses involving freedom of speech. The coalition’s junior partner, the far-left United We Can party, has filed a petition to pardon Hasél.

Eight suspects have been jailed for being in a group that protested the rapper’s imprisonment by setting fire to a police van in which an officer narrowly escaped the flames.

They face possible charges of attempted homicide, assaulting law enforcement officers and forming part of a criminal group.