Spain dismissed Catalonia's president and Cabinet and dissolved its Parliament on Friday hours after lawmakers in the region voted overwhelmingly to declare independence.
"In this moment, we need to be serene and careful, but we also need to have confidence that the state has the tools, backed by the law and reason, [to] peacefully and reasonably go back to legality and take away threats to democracy," Spanish Prime Minister Mariano Rajoy said.
Earlier, the Catalan Parliament voted overwhelmingly in favor of independence, prompting the Spanish Senate to grant Madrid unprecedented powers to seize control of the autonomous region.
The day's dramatic and fast-moving events pushed Spain into uncharted territory, testing the limits of the constitution drawn up after the restoration of democracy in the 1970s.
Amid extraordinary scenes in the regional capital of Barcelona, Catalan lawmakers voted to "form the Catalan Republic as an independent and sovereign state" by 70 to 10.
Dramatic scenes in BarcelonaOpposition parties walked out of the chamber just before the vote, a culmination of a weeks-long standoff with Madrid that began with a disputed referendum on October 1.
Supporters of independence gather outside the Catalan Parliament in Barcelona.
Pro-independence crowds massed outside the Parliament cheered and waved the Catalan separatist "Estelada" flag as the result was announced.
Less than an hour later, the Spanish Senate granted the Madrid government powers under Article 155 of the Constitution to sack the Catalan President Carles Puigdemont and his ministers.
The Spanish government called two Cabinet meetings for later Friday. Rajoy has pledged to quash the separatists, and moves to take over the Catalan administration are expected to begin at the weekend.
"Spain is a serious country, a great nation and we will not allow some people to blow up our Constitution," Rajoy told journalists in Madrid.
He urged Spanish citizens to remain calm, saying that the government will respond to the situation in a "proportionate way."
"The government will make any decisions needed to go back to legality, and we will do that this evening," he said.
Spain's general prosecutor confirmed it would file a lawsuit for rebellion against Puigdemont, the Catalan government and the members of the parliament board who voted in favor of independence.
Puigdemont: 'Stay strong'Speaking in the Catalan Parliament building after the landmark vote, Puigdemont said legitimately elected lawmakers had cast their ballots according to a mandate earned in the October 1 referendum.
But he acknowledged that the path ahead would not be easy. "We are facing a period in which we will need to stay strong and in peace, dignified and civil as we have always been, and I'm sure we will keep being so," he said.
"The institutions and the people together built nations, societies, and a nation cannot be built without one of these elements."
Supporters followed his words with applause and repeated chants of "freedom, freedom."
Rajoy: No other wayAddressing the Spanish Senate ahead of its vote on Article 155, Rajoy said the rule of law had been "stomped on" in Catalonia and warned of a fracturing of society.
"Exceptional measures need to be adopted when there are no other ways to go back to normality," he said.
Those measures are "not against Catalonia but aiming to stop Catalonia being abused," he said. "Not to suspend the autonomy of Catalonia but to consolidate it; not to cut back rights but to restore them to legality. What's threatening Catalonia is not Article 155 but the behavior of the government of Catalonia."
It was unclear on Friday how the Spanish government would use its powers. A tough crackdown could risk a repeat of the violent scenes that played out on October 1, the day of the referendum.
But it seemed unlikely that members of the Catalan government who have fought so hard for independence would simply acquiesce to Spanish government forces.
Another question was how the local Catalan police force would react if national forces were deployed to the streets of Barcelona.
International reactionThe European Union has backed Madrid in its handling of the crisis, which Rajoy has insisted is an internal matter.
Following the Catalan Parliament's vote, European Council President Donald Tusk tweeted: "For EU nothing changes. Spain remains our only interlocutor. I hope the Spanish government favours force of argument, not argument of force."
Puigdemont responded via Twitter: "Catalans always favour the force of arguments."
The UK and Germany, through government spokesmen, said they would not recognize Catalonia's independence declaration.
The United States also voiced its support for the Madrid government.
"Catalonia is an integral part of Spain, and the United States supports the Spanish government's constitutional measures to keep Spain strong and united," US State Department spokeswoman Heather Nauert said in a statement.