MADRID — The Spanish police detained more than a dozen people in the region of Catalonia on Wednesday, drastically escalating tensions between the national government and Catalan separatists. The episode occurred less than two weeks before a highly contentious referendum on independence that the government in Madrid has vowed to block.

With the backing of the constitutional court, Prime Minister Mariano Rajoy has been stepping up efforts to prevent the referendum, scheduled for Oct. 1.

The police raided the offices of the Catalan regional government early Wednesday and arrested at least 14 people, including Josep Maria Jové, secretary general of economic affairs. The arrests were not expected, but hundreds of mayors and other officials in Catalonia had been warned that they would be indicted if they helped organize a referendum in violation of Spanish law.