Fueled by economic grievances and a distinct language and culture, aspirations for an independent state in Catalonia have ebbed and flowed for generations.
But the current confrontation has presented a vexing quandary not only for Spain but the entire European Union, pitting demands for self-determination against the desire to preserve the sovereignty and territorial integrity of an important member state.
Mr. Rajoy took the bold steps with broad support from Spain’s main political opposition, and will almost certainly receive the required approval next week from the Spanish Senate, where his own conservative party holds a majority.
He did so despite repeated appeals for dialogue and mediation by the Catalan leader, Carles Puigdemont, whose independence drive has been shunned by wary European Union officials.
Mr. Rajoy said the Catalan government had never offered real dialogue but had instead tried to impose its secessionist project on Catalan citizens and the rest of the country in violation of Spain’s Constitution.
He said his government was putting an end to “a unilateral process, contrary to the law and searching for confrontation” because “no government of any democratic country can accept that the law be violated, ignored and changed.”
Mr. Rajoy said he planned to remove Mr. Puigdemont, and the rest of his separatist administration from office. The central government was also poised to take charge of Catalonia’s autonomous police force and the Catalan center for telecommunications.
Mr. Rajoy did not ask to dissolve the Catalan Parliament, but instead said that the president of the assembly would not be allowed to take any initiative judged to be contrary to Spain’s Constitution for a period of 30 days, including trying to propose another leader to replace Mr. Puigdemont.
Mr. Rajoy said that his goal was to arrange new Catalan elections within six months, so as to lift the measures taken under Article 155 as soon as possible.
It’s unclear, however, how such elections would be organized or whether they would significantly change Catalonia’s political landscape, let alone help to resolve the territorial conflict.
Mr. Puigdemont led a mass demonstration of 450,000 people in Barcelona, the region’s capital, on Saturday afternoon.
In a televised address late Saturday, Mr. Puigdemont said he would convene Parliament next week to discuss the response to Mr. Rajoy; he did not rule out using the session to declare independence. He accused the Spanish government of trying to “eliminate our self-government and our democracy.”
In a part of his speech delivered in English, Mr. Puigdemont also addressed Europe’s politicians and citizens and suggested Europe’s “foundational values are at risk” in the dispute with Madrid. “Democratically deciding the future of a nation is not a crime,” he argued.
Other Catalan separatist politicians warned that Mr. Rajoy’s announcement would escalate rather than resolve the conflict.
Josep Lluís Cleries, a Catalan Senator, told reporters on Saturday that Mr. Rajoy was suspending not autonomy in Catalonia but democracy.
Carme Forcadell, the separatist president of the Catalan Parliament, pledged on Saturday evening to defend “the sovereignty” of her assembly. “We will not take a step back,” she told a news conference. “Mr. Rajoy isn’t conscious that by attacking the institutions, he is attacking the society of this country.”