An Argentine human rights group said Thursday it would file a petition with the European Court of Human Rights to try to halt a trial of a Spanish judge for investigating Franco-era atrocities.

"This habeas corpus has the goal of putting an end to the iniquitous persecution of Baltasar Garzon," Eduardo Barcesat, a lawyer for the Mothers of the Plaza de Mayo, told AFP.

The group was formed by relatives of the thousands of people who disappeared in secret prisons during Argentina's "dirty war" more than three decades ago, abuses reminiscent of those that occurred during the Spanish civil war.

Garzon, whose investigations led to the arrest of Chilean dictator Augusto Pinochet in Britain in 1998, was accused of abuse of power when he opened a similar investigation into murders and disappearances under Spanish dictator Francisco Franco.

He is now on trial in Madrid after two right-wing Spanish groups alleged he violated the law by failing to abide by a 1977 amnesty.

Barcesat said the habeas corpus petition to be filed next week with the European Court of Human Rights would be a first, because such a recourse is normally filed with national courts.