In 2015, the court declared regional independence referendums to be unconstitutional. Protesters said they hoped the vote would go ahead as planned on October 1.
The pro-independence coalition ruling Catalonia has vowed to hold the vote despite the prohibition and has asked the 947 mayors in the northeastern region to provide facilites for the plebiscite.
This handout picture released on September 11, 2017 by the Assemblea Nacional Catalana (Catalan National Assembly) shows an aerial view of people waving a giant "Estelada" (pro-independence Catalan flag) and a giant banner depicting a ballot box and reading in Catalan "Referendum is democracy" during a pro-independence demonstration, on September 11, 2017 in Barcelona during the National Day of Catalonia, the "Diada".
The mayors in question have all publicly pledged their support for the referendum and they represent around 75 percent of all Catalan mayors.
Police have searched a Catalan printing house and a local weekly newspaper suspected of making ballots for the referendum, while Spain's state prosecutor has opened criminal proceedings against Puigdemont and other Catalan officials.
Prosecutors have already launched an official complaint against Catalan President Carles Puigdemont and members of his government over their referendum plans, accusing them of civil disobedience, misfeasance and misappropriation of public funds - the latter carrying jail sentences of up to eight years.
Spanish court blocks second law linked to Catalan referendum
Rajoy's conservative government argues the vote violates the constitution, which states that only central authorities can call a referendum.
Spain's top court has suspended the law that was meant to become Catalonia's transitional constitution if the region declares itself a separate nation, according to reports.
Mr Rajoy said today: "If anyone urges you to go to a polling station, don't go, because the referendum can't take place, it would be an absolutely illegal act".
In his first comments on the growing political crisis, Felipe said the rights of all Spaniards will be upheld against "whoever steps outside constitutional and statutory law".
The economically powerful Catalonia has a thriving population of 7.5 million and accounts for a fifth of Spain's economic output.
Thousands of Catalan separatists rallied on Monday to demand their region break away from Spain, in a show of strength three weeks ahead of an independence referendum banned by Madrid.