The people of Catalonia in north-eastern Spain voted in a poll on independence on Sunday.
The Spanish judiciary has ruled the vote unconstitutional but Catalan leader Artur Mar warned against any attempt to disrupt it.
Spain’s constitutional court suspended earlier plans for a referendum on secession, according to the BBC.
Prime Minister Mariano Rajoy said the vote would have no effect and urged the region to return to “sanity”.
Voters will be asked whether they want a Catalan state and whether that state should be independent.
Opinion polls show that as many as 80 percent of Catalans want more autonomy from Spain, with about 50 percent in favor of full independence.
‘Attack on Democracy’
Catalonia is a wealthy a region of 7.5 million people and contributes more to the Spanish economy than it gets back through central government funds. Economic and cultural grievances have fuelled Catalan nationalism.
Analysts say many Catalans have always felt that they do not quite fit in a unitary state.
They says there is a long history of support for winning independence from Spain, or at least much greater autonomy within it.
This week, the Constitutional Court demanded the vote be suspended.
But Catalonia’s government insisted it went ahead, organized by volunteers and with no official electoral roll.
Mas warned the Spanish government against any attempt to halt the vote.
He said: “I don’t know what they will do, it does not depend on us, but if they have a minimum of common sense I think any action out of the ordinary would be a direct attack on democracy and a direct attack on fundamental rights.”
Rajoy urged a return to sanity and for talks “within the legal framework of the constitution”.
He said the vote would be “neither a referendum nor a consultation nor anything of the sort”.
He added: “What is certain is that it will not have any effect.”
Catalonia adopted a charter in 2006 giving it “nation” status but this was overruled by the Constitutional Court in 2010.
