Some of the mayors gathered with Catalan President Carles Puigdemont outside the headquarters of the regional government, the Generalitat Palace, as supporters waved the lone-star flag of the independence movement, the report said.
"Barcelona Mayor Ada Colau, who supports the right to hold the referendum, also turned up".
Earlier, Spain's Constitutional Court suspended legislation passed in the Catalan parliament which paved the way for the vote.
The Catalan government has been scrambling to press ahead with the vote, despite the central government's warnings that local municipalities are not allowed to use public buildings and mayors can be legally prosecuted for it.
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The nationalist protests are not only a show of solidarity with Catalonia's mayors, but a push back on several Spanish government attempts to censure the referendum that Catalan lawmakers announced on September 6.
Armed police have raided print works and newspaper offices in Catalonia in search of voting papers and ballot boxes to be used in the referendum - to no avail. Organizing the referendum will be almost impossible without the cooperation of local municipalities.
"They want to denounce the anti-democratic attitude of the Spanish state", she added. City authorities have been forced to sign an agreement that federal money will not be used for referendum purposes.
Catalonia is sharply divided, with a government poll in July finding that 41.1 percent of people were for and 49.4 percent against independence, although the vast majority agree to holding a referendum to decide the matter. Madrid has threatened to strip Catalonia of its budget if any funds are channeled to the referendum. "Of course, we would respect them", he said, adding that even though Catalonia might not immediately become an European Union member state, in the end, the people and companies would change nothing but their nationality.