Radical Basque separatists will not be able to field candidates in Basque regional elections for the first time, Spain's Supreme Court said in a ruling announced overnight, dpa reported.
The court barred the Askatasuna and D3M parties from of the March 1 poll on grounds of links with the militant Basque separatist group ETA, which has killed more than 800 people since 1968.
D3M and Askatasuna had emerged as successors to three other outlawed separatist parties.
ETA's political wing Batasuna, which had taken about 10 per cent of the Basque vote, was outlawed in 2003.
Its successors Basque Nationalist Action (ANV) and the Communist Party of Basque Lands (PCTV-EHAK) were made illegal in 2008.
The Spanish government and the public prosecutor's office had sought bans on D3M and Askatasuna in what was seen as a strategy to crack down on the entourage of ETA, in addition to the group itself.
If the Constitutional Court confirms the ban, radical Basque separatists will be left without representation in regional elections for the first time.
ETA is listed as a terrorist organization by the European Union and the United States.