Spanish riot police burst into polling stations across Catalonia on Sunday, confiscating ballot boxes and voting papers to try to halt a banned referendum on a split from Spain as Madrid asserted its authority over the rebel region.

The Mayor of the regional capital Barcelona Ada Colau issued a statement demanding an immediate end to police charges against the defenseless population. Madrid said its police had acted in a proportionate manner.

Police broke down doors to force entry into voting stations as Catalans shouted Out with the occupying forces! and sang the anthem of the wealthy northeastern region. In one incident in Barcelona, police fired rubber bullets.

Officers in riot gear hit people with batons and forcibly removed would-be voters, including women and the elderly, from polling stations.

Catalan officials said over 700 people had been injured in the police crackdown.

Central governments representative in Catalonia Enric Millo, referring to police action, told a news conference: We have been made to do something we didnt want to do.

The referendum, declared illegal by Spains central government, has thrown the country into its worst constitutional crisis in decades and deepened a centuries-old rift between Madrid and Barcelona.

It remained unclear what action the Catalan government might take. However much voting takes place, a yes result is likely, given that most of those who support independence are expected to cast ballots while most of those against it are not

Despite the police action, hundreds-strong queues of people formed in cities and villages throughout the region to cast their votes. At one Barcelona polling station, elderly people and those with children entered first.

Im so pleased because despite all the hurdles theyve put up, Ive managed to vote, said Teresa, a 72-year-old pensioner in Barcelona who had stood in line for six hours.

The ballot will have no legal status as it has been blocked by Spains Constitutional Court and Madrid for being at odds with the 1978 constitution.

A minority of around 40 percent of Catalans support independence, polls show, although a majority want to hold a referendum on the issue. The region of 7.5 million people has an economy larger than that of Portugal.