Thousands of people have rallied in the Basque city of Bilbao in northern Spain to demand the legalisation of a new separatist party called Sortu.
Its backers are members of the political wing of the Basque militant group Eta.
Sortu's predecessor Batasuna was banned in 2003 by Spanish courts.
Eta has killed more than 800 people, many of them Spanish police officers, in fighting for an independent Basque state over the past four decades.
Sortu's backers say they now reject the use of violence and are committed to fighting for independence through purely political means.
Correspondents say many Spaniards are unconvinced, saying it is a tactical and temporary ploy forced on ETA because it is now weaker than ever.
But in Bilbao, they add, there is a sense this marks a significant step on the path to a lasting peace.