Three backers of Catalonia's independence have sought to secure release from jail for their role in the region's push to break from Spain which triggered the country's worst political crisis in decades.

Officials are determined to proceed with Sunday's vote, even though Spain's government says it is illegal.

Spain's central government and regional Catalan authorities argued on Saturday over who controls the regional police force that is considered key to the success of a planned independence vote for the north-eastern region.