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.