On Monday Baltasar Garzon charged Joseba Permach and Joseba Alvarez - members of the nationalist Basque party Sozialista Abertzaleak - of having ETA membership and ordered they stand trial.

Basque lawmakers formed Sozialista Abertzaleak after Spanish authorities banned Batasuna in 2003, considering it to be the political wing of ETA and responsible for more than 800 deaths in a four-decade struggle for an independent Basque state.

Baltasar also issued an international arrest warrant for former Batasuna deputy Jose Antonio Urruticoetxea, "Josu Ternera", currently on the run.

Urruticoetxea, a former high-ranking ETA official, is believed to have resumed an influential role in the organisation.

Ongoing inquiry

Last month, Garzon charged 36 suspected Batasuna members with ETA membership, as part of his ongoing investigations of ETA and its allies.

ETA is blamed for bombings that
have claimed 800 lives to date

Batasuna is regarded as a terrorist organisation by the US State Department and the European Union.

Garzon, who gained international attention for the arrest in 1998 in London of former Chilean military dictator Augusto Pinochet, left later Monday for New York where he will teach courses on international terrorism for nine months.

Earlier this month, the Basque premier, Juan Jose Ibarretxe, brought forward regional elections to revive his stalled plan for virtual independence from Spain.   

A day after the Spanish parliament rejected Ibarretxe's plan for "free association" with Spain, the Basque leader called elections for 17 April and vowed to call a referendum on his proposal if he wins.   

Such a referendum, without the blessing of Spain's parliament, would be a major challenge for Spanish Prime Minister Jose Luis Rodriguez Zapatero, who has adopted a conciliatory approach towards the Basques.