Pablo Hasel, a previously obscure artist in the Spanish rap scene, is now at the centre of a battle over free speech in the country.
Several hundred protesters took to the streets of Barcelona on Saturday to demand the release of rapper Pablo Hasel and his jailed supporters.
Saturday's march took place amid a heavy police presence, winding through several avenues of the Catalan regional capital.
The musician is serving nine months for inciting terrorism and for refusing to pay a fine for insulting Spain's former king.
He has praised Grapo and ETA, two now-defunct armed groups responsible for killing over 900 people in Spain.
His arrest on February 16 triggered a wave of 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.
The ruling left-wing coalition has pledged to launch a legal reform to eliminate prison terms for offences involving freedom of speech.
The coalition's junior partner, the far-left United We Can party, has filed a petition to pardon Hasel.
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.