Spain's state prosecutor's office says it will present criminal charges against members of the Catalan parliament who voted in favour of the region holding a referendum on independence.
The regional parliament, which is controlled by pro-independence parties, adopted the so-called "referendum bill" in an acrimonious session on Wednesday, with 72 votes in favour and 11 abstentions
Jose Manuel Maza, the state prosecutor general, said on Thursday that he had asked security forces to investigate any preparations by the Catalan government to hold the referendum in October.
He said two different lawsuits are being prepared: one that seeks to punish the MPs who allowed the debate and vote on the legal framework of the planned referendum, and a separate one against the executive branch of the regional government, whose members officially called the October 1 vote.
Mariano Rajoy, the Spanish prime minister, called Wednesday's vote an "intolerable act of disobedience" on Thursday.
In a statement to reporters, Rajoy said he would ask Spain's constitutional court to revoke the referendum law, and told Catalan civil servants: "No one can make you do anything illegal".
Catalonia, an area of 7.5 million people with its own language and culture, accounts for about 20 percent of Spain's economic output and has significant powers over matters such as education, healthcare and welfare.
Speaking earlier this week, Rajoy said his government would not allow the territory to become independent.
"The Catalonians cannot carry out this referendum as planned because they are not allowed to do so either by the Constitution or existing law," he said.
According to the Spanish constitution, referendums on sovereignty must be held nationally, not regionally.
Source: News agencies