Barcelona, Spain (CNN) The Spanish government has taken its first steps to impose direct rule on Catalonia, firing its police chief and nominating the deputy prime minister to take control of the region in an unprecedented effort to quash its attempts at secession.

A day after the Catalan parliament defied Madrid and voted for a unilateral declaration of independence , Spanish Prime Minister Mariano Rajoy issued a decree that confirmed the sacking of Josep Lluís Trapero, head of the regional police force, the Mossos d'Esquadra.

Trapero already faced charges of sedition over his force's actions in the run-up to Catalonia's banned October 1 independence referendum. The director general of the Catalan police, Pere Soler, was also dismissed.

On Friday Rajoy dismissed Catalonia's president and cabinet, dissolved its parliament and called new elections for December 21 as part of a drastic package of measures to seize control of the renegade administration in Barcelona.

Rajoy appointed his Deputy Prime Minister, Soraya Sáenz de Santamaría, to take charge of Catalonia's government.

It remains unclear how the Spanish government will enforce the measures announced by Rajoy. A tough crackdown could risk a repeat of the violent scenes that played out in Catalonia on October 1, the day of the disputed referendum, when national police were brought in.

Much also depends on whether Catalonia's deposed leaders give up their power willingly, and whether the thousands of civil servants in the region carry out orders issued by Madrid.

In a televised address Saturday, dismissed Catalan President Carles Puigdemont appealed for Catalan citizens to remain peaceful and use "democratic opposition" to advance their cause.

"Let's move forward with the only winning attitude -- without violence, insults, in a very inclusive way, respecting opinions and symbols and protests by other people who are against what the parliamentary majority decided," he said.

"I ask you to have patience, perseverance and perspective. The best way to defend the point we have reached now is the democratic opposition to Article 155," he added, referring to the constitutional provision which allowed Madrid to impose direct rule.

Catalan police: Remain neutral

The Catalan Police Prefecture circulated a letter internally asking the Mossos to remain neutral as events unfold.

"We must remember that in each and every one of our interventions, we are acting as representatives of the institution we serve and not as individuals. Consequently, the principle of neutrality must always be upheld," said the letter, whose authenticity was confirmed to CNN by the Mossos.

If demonstrations bring those with opposing views into conflict, the force's responsibility "is to guarantee everyone's safety and to prevent any incidents from happening," the letter said, adding that mediation was the best tool.

Protesters with Catalan separatist flags celebrate in Barcelona on Friday.

In a separate internal document, whose authenticity was also confirmed to CNN by the Mossos, Soler said the Catalan police force was being treated in an "extraordinarily unjust manner."

Soler said the Catalan police were being "falsely accused" of a lack of preparation ahead of the controversial referendum, adding that the actions of the Mossos' officers "were more efficient without injuring anyone in any case."

In another letter circulated within Mossos, which confirmed its authenticity, Trapero spoke of his "sadness" over his dismissal but called on the force to go on doing its job.

"You have to keep on building the future. The commanders who take over will help you do that, and I ask you to do what you always did, to be loyal and understanding with their decisions," he said.

Trapero's deputy, Ferrán Lopez, has been appointed to head the Catalan force in his place, under the authority of the Spanish Interior Ministry.

Dismissed Catalan police chief Josep Luis Trapero, pictured on October 16, is accused of sedition.

The Spanish government's moves came hours after the Catalan Parliament voted to "form the Catalan Republic as an independent and sovereign state." Opposition lawmakers boycotted the vote.

There were wild celebrations in the streets of Barcelona, the regional capital, by those who back secession on Friday night. Rival demonstrations into the night were held by those who favor unity with Spain.

The secessionist movement has deeply divided Catalonia, one of Spain's wealthiest regions. Some 90% voted in favor of independence in the disputed referendum, but turnout was only 43%.

Anti-independence demonstrators gathered in Madrid on Saturday to call for unity. Many held Spanish flags aloft, while others carried placards saying "No to the coup!" or calling for Puigdemont to go to prison.

People hold signs reading "No to the coup" while waving Spanish flags during a demonstration urging unity in Madrid on Saturday.

Appeal for calm

Both the Spanish government and Catalan leaders have appealed for calm amid heightened tensions on both sides.

The front pages of national and regional Catalan newspapers on Saturday illustrated the depth of the divisions.

The headline on Catalan daily El Punt Avui declared "Hello Republic," with images of celebrating crowds outside the Catalan Parliament and the motion for independence approved by its lawmakers. Another Catalan daily, Ara, had the headline "The Republic, proclaimed, the government, sacked."

Meanwhile, national daily El Pais ran a headline reading "The State on its way to put out the insurrection," while fellow national daily ABC's front page declared "Spain beheads the coup."

Rajoy said Friday the government's moves were needed to restore legality and protect the nation. Article 155 has never before been used.

Earlier, Puigdemont said legitimately elected lawmakers had cast their ballots according to a mandate earned in the October 1 referendum.

Catalan President Carles Puigdemont casts his vote for independence from Spain on Friday.

How did we get here?

The dispute is Spain's worst political crisis since democracy was restored in the 1970s. It was triggered by the decision of Catalonia's political leaders to push ahead with the October 1 independence referendum, even after it was banned by Spain's highest court.

The plebiscite was the culmination of a yearslong effort by secessionists in Catalonia, which has its own distinct culture and language.

Despite calls for dialogue, the opposing sides have been at loggerheads since the vote, with neither apparently willing to give way.

After Puigdemont declined to clarify to Madrid whether he had declared independence following the referendum, the Spanish government pushed ahead with plans to impose direct rule under Article 155. Two leading figures in the secessionist movement, Jordi Sànchez and Jordi Cuixart, were also detained on sedition charges.

The standoff culminated in Friday's dramatic events. But Spain and Catalonia now enter uncharted territory.

The European Union has made it clear that it does not support the move, fearing breakaway movements in other member states. In any case, under EU rules, Catalonia would not be a member of the EU on its own, and would have to apply for membership from outside the bloc.

Germany, France, the United Kingdom, Ireland and the United States issued statements saying they would not recognize the independence of Catalonia.