In a written statement, the Galician Nationalist Bloc described Israeli action as "piracy".
The bloc's spokesman Francisco Jorquera and Rosana Peres, a parliament member, also criticised the Spanish government's reaction over the incident, which saw Israeli forces taking by force the civilian vessel, Marianne, to the Israeli port of Ashdod.
Spanish Member of the European Parliament Ana Miranda, who was on board Marianne but now back in Spain, also spoke in the Spanish parliament earlier today.
The spokesman called on Spain's Foreign Ministry to take a tough stance over the incident and face the Gaza issue head on.
Podemos's spokesman Rfael Mayoral also urged the international community to raise its voice against Israel.
Mayoral emphasized that Israel should end its "discrimination" and "blockade" on Gaza underling that Israel violated human rights.