Spain's King Felipe addressed the nation on Tuesday
The Catalonian police chief is set to appear before a Spanish court on Friday to answer questions about how he handled election protests there.
The court is to examine whether he and his colleagues should be charged with sedition - a charge of inciting people to rebel against the State.
The head of the Catalonian government Carles Puigdemont says the region will declare independence by early next week.
Spanish broadcaster TVE says the Catalonia parliament will hold a plenary session next Monday, in which it could declare independence.
Last night, Spain's King Felipe addressed the nation on TV, and called Catalonia's independence referendum "illegal" and "undemocratic".
It came after thousands demonstrated across the region in reaction to police violence during the vote on Sunday.
King Felipe said: "Today Catalan society is fractured and in conflict," he said - referring to the crisis as a "very serious moment for our democratic life."
He also accused Catalan politicians of shattering democratic principles and of dividing society.
"They have violated the democratic principles of the rule of law and they have undermined the harmony of Catalan society," he said.
The response of Spanish authorities to the referendum. including rubber bullets and batons, has prompted discomfort internationally and fury in Catalonia.
Catalonia's government said that of the 2.2 million voters who were able to cast ballots, two million voted for independence.
The United Nations says human rights experts should be allowed to visit the region, after officials claim 844 people were injured.
UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said: "I am very disturbed by the violence in Catalonia on Sunday.
"With hundreds of people reported injured, I urge the Spanish authorities to ensure thorough, independent and impartial investigations into all acts of violence.
"Police responses must at all times be proportionate and necessary.
"I firmly believe that the current situation should be resolved through political dialogue, with full respect for democratic freedoms.
"I call on the government of Spain to accept without delay the requests by relevant UN human rights experts to visit."
On Monday, Taoiseach Leo Varadkar said Ireland will not recognise the referendum result.
Additional reporting: Jack Quann