Spain's National Court is to question two senior officers from Catalonia's regional police force and the leaders of two pro-Catalan independence civic groups who have been placed under investigation for sedition.

The court said that the four will be quizzed on Friday about their roles in demonstrations in Barcelona on September 21 and 22 when Spanish police arrested several Catalan government officials and raided offices in a crackdown on preparations for last weekend's referendum on Catalonia's independence.

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Spanish authorities said the demonstrations hindered the police operation. During the rallies, there were some disturbances and two police vehicles were wrecked.

The four include regional police chief officer Josep Lluis Trapero and Jordi Sanchez, the head of the Catalan National Assembly, which has been the main civic group behind the independence movement.

Sunday was marred by scene of brutal police violence as Spain tried to crack down on Catalonia's attempt to hold a peaceful vote. Despite this, two million Catalans, 90% of those who turned out, voted Yes.

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President Carles Puigdemont said last night that Catalonia will declare independence from Spain in a matter of days, .

In his first interview since Sunday’s referendum, Puigdemont told the BBC that his government would “act at the end of this week or the  beginning of next”.

When asked what he would do if Madrid was to intervene and take control of Catalonia’s government, Puigdemont said it would be “an error which changes everything”.

Puigdemont spoke after an extra-ordinary television address by Spain’s king, Felipe VI, who claimed the Catalan authorities had deliberately bent the law with their “irresponsible conduct”.

The king complained the independence referendum was “undemocratic”  and said that “the state needs to  ensure constitutional order and the rule of law in Catalonia.”

Felipe spoke out after tens of thousands of people joined in marches across the city of Barcelona in protest against the Spanish government’s  actions over the independence vote.

The king said that the bid by the authorities in Catalonia “undermined coexistence”. “Today, Catalan society is fractured and confronted,” Felipe said, referring to the political crisis as “very serious moments for our  democratic life”.