The Spanish government on Monday formally asked the constitutional court to declare illegal Catalonia's planned vote on independence from Spain, Prime Minister Mariano Rajoy said in a televised statement.
"Neither the object nor the proceedings of the vote are compatible with the Spanish constitution," Rajoy said after the president of Spain's Catalonia region, Artur Mas, on Saturday called the vote for Nov. 9.
A long-standing pro-independence movement in the north-eastern region has gathered momentum during recent years of economic hardship.
A large majority of the 7.5 million Catalan population favors the independence poll.