MADRID -- Spain asked the Supreme Court on Tuesday to outlaw radical Basque Party Batasuna over its alleged support of armed group ETA, setting the stage for possible clashes at banned pro-Batasuna protests this weekend.

The lawsuit was filed after the Spanish Parliament voted on August 26 to seek to dissolve the party because it refuses to condemn violence by ETA, Western Europe's most active guerrilla group which has killed 836 people in 34 years.

Spain's Justice Minister Jose Maria Michavila displayed 26 boxes he said were packed with 1,000 pieces of evidence linking Batasuna and ETA and singling out 194 of the party's political leaders he said also belong to ETA.

"This is what our democracy demands. The lawsuit is the instrument called for in the law in order to protect the victims of terrorism, a law that puts an end to impunity for those who use the privileges of political parties in order to serve violence," Michavila told a news conference.

"Batasuna is the prolongation of terrorism ... the prolongation of ETA," Michavila said.

Batasuna shares ETA's vision of Basque independence but denies it is ETA's political wing.

The Supreme Court is Spain's second highest, leaving Batasuna the opportunity to appeal to the Constitutional Court should the Supreme Court rule in favor of the government.

The party received 143,000 votes or 10 percent of the total in last year's Basque parliamentary elections -- its worst showing ever -- and also has some support in Navarre outside the three official provinces of the semi-autonomous Basque country.

Batasuna supporters said on Tuesday they would go ahead with street demonstrations called for this Saturday in Bilbao, the largest Basque City, and for Sunday in San Sebastian, a bastion of Basque nationalism, even though the Basque region's interior department on Monday prohibited the marches.

Their pledge to go ahead regardless raises the possibility of clashes.

The Basque government said it decided not to allow the protests after a demonstration on Sunday in San Sebastian turned violent and featured shouts in support of ETA.

After the march ended peacefully, Basque riot police clashed with masked Batasuna supporters in the narrow streets of central San Sebastian. A local man who was not part of the demonstration lost an eye when police fired rubber bullets at demonstrators hurling bottles and smashing storefronts.

Spanish police have been shutting down the offices and property of Batasuna on orders from High Court Judge Baltasar Garzon, who suspended the party's activities for at least three years last week, accusing it of funding and helping ETA.