A Spanish court has suspended a Catalan law that outlined a legal framework for an independent state, a day after hundreds of thousands rallied in Barcelona to support secession from Madrid.

Prime Minister Mariano Rajoy's government is increasing the pressure to prevent an independence referendum, scheduled for Oct. 1, from going ahead. It has declared the vote illegal and challenged laws linked to the ballot in the courts.

The Constitutional Court, Spain's highest authority on such matters, suspended the law while judges consider whether it is against the country's constitution. It suspended a law approving the Oct. 1 vote last week.

The Catalan parliament approved both laws on Wednesday in a move which brought a long-running tussle between the pro-independence regional government and the Madrid-based central government to a head.

Rising tension between Madrid and Barcelona has prompted some investors to ditch Spanish sovereign debt.

Catalan leader Carles Puigdemont, who faces criminal charges for his role in organising the referendum, only has the power to call an election not a referendum, a government spokesman said on Tuesday.

"If Puigdemont wants to consult the people, it's very simple, he should call an election," government spokesman and Minister of Education, Culture and Sport Inigo Mendez de Vigo told Antena 3 television.

Polls have shown support for independence waning in recent years with those wanting a separate state in a minority. However, a majority of Catalans want to vote on the issue.

Most of Catalonia's 948 mayors have pledged to permit use of public spaces for the vote, but Ada Colau, head of the region's biggest city Barcelona, has asked for assurances that civil servants involved will not risk losing their jobs.

Justice Minister Rafael Catala warned the regional administration against coercing municipal leaders to take part.

"I trust they will be left in peace and not be obliged to do what they cannot," Catala told RTVE television.