The Catalan regional government has accused the Spanish authorities of behaving like Turkey, China and North Korea by blocking websites designed to help people vote in Sunday's independence referendum.

Over the past week the Spanish government has stepped up its efforts to stop the unilateral vote by deploying thousands of extra police officers to Catalonia and taking control of the region's finances.

It insists the referendum is illegal and a clear violation of the Spanish constitution.

The Catalan high court has assumed control of efforts to prevent the vote, instructing local and national police officers to stop public buildings being used as polling stations and to seize any material related to the referendum.

On Wednesday evening, Judge Mercedes Armas said the court would take over from the regional prosecutor, adding that recent events had shown that Catalonia's pro-independence government had "clearly breached" the constitutional court rulings prohibiting this Sunday's vote.