Dozens of campaigners have gathered in central Madrid, calling for justice for family members who were victims of Spanish dictator Francisco Franco’s regime.
The Spanish Amnesty Law of 1977 prevents any Franco-era crime from being put to trial.
Last week, in a move that was hailed as victory by relatives of the victims, a judge in Argentina issued an international arrest warrant for four of Franco’s former commanders last week.
Now, Spanish High Court Judge Pablo Ruz has launched an investigation into whether to authorise the extradition of the men, who are accused of murder and torture.
Court sources indicate that two of the men – Franco’s former bodyguard Celso Galvan and ex-police commissioner Jose Ignacio Giralte have died.
The other two men – former Civil Guard officer Jesus Munecas, 74, and ex-police inspector Jose Antonio Gonzalez Pacheco, 67, are due to be summoned by Ruz for questioning.