THE Spanish prime minister Mariano Rajoy will sack the Catalan Government and force early elections, as his government seeks unprecedented constitutional authority to "restore order" in Catalonia.

Rajoy's held an extraordinary meeting of ministers, and has now invoked Article 155 of the Spanish Constitution.

The previously untapped article allows central authorities to intervene when one of Spain's 17 autonomous regions fails to comply with its law.

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Although the ruling Popular Party has enough majority to get the specific measures passed by the country's Senate, Rajoy has gained the support of the opposition to revoke Catalonia's autonomy.

He has proposed having central government ministers assume the powers of Catalan officials.

Rajoy can force the removal of officials and plans the early Catalan elections within six months.

He claimed the government is not revoking Catalonia's autonomy, only removing officials who violated the law.

The article has never been used since the 1978 Constitution was adopted, but Rajoy's conservative government said establishing direct control over Catalonia is a move of last resort.

The goal is "the return to legality and the recovery of institutional normalcy", the prime minister had said on Friday.

Rajoy's proposed actions are expected to spark angry opposition from supporters of independence and moderate Catalans.

Catalan leader Carles Puigdemont plans to join an afternoon protest before delivering a speech in response to the Spanish government's decision to take over the regional cabinet's functions, officials in Catalonia said.

In the streets of Barcelona, banging pots and pans and honking cars greeted Rajoy's announcement.

At the national level, Pablo Echenique, a secretary in the far-left Podemos party, vowed to work to oust Rajoy and his conservative Popular Party.

Pro-business Ciudadanos (Citizens) party president Albert Rivera says he supports the announced measures to heal divisions created by the Catalan independence movement and to provide the security companies need to remain in Catalonia.

Spanish opposition parties have agreed to support the prime minister in revoking Catalonia's autonomy as a way to thwart the independence drive.

Catalan leader Carles Puigdemont earlier threatened to call a vote in the Catalan parliament for an explicit declaration of independence from Spain.

Meanwhile, a spokeswoman for Spain's Constitutional Court said the court's website has been affected by a cyber attack of unknown origin.

The attack came as social media accounts linked to the Anonymous group launched a campaign to "free Catalonia".

The spokeswoman said it only affected the court's website and no internal information was compromised.

Spain's National Security Department said on Friday that an undisclosed number of government websites had been hit in recent weeks with slogans supporting independence for Catalonia.

In a YouTube video posted by an account linked to Anonymous, the group announced actions that would be rolled out today as part of "Operation Free Catalonia".