Catalonia referendum: Firefighters attacked by Spanish police as they form human shield to protect voters

International condemnation grows as images of authorities' aggressive response spread

Spanish police have been filmed apparently attacking Catalan firefighters who had formed a human shield around people trying to vote in the region's independence referendum.

Footage posted on social media appeared to show several riot officers kicking and using batons to beat men in firefighters' uniforms, amid growing violence in Barcelona and surrounding districts.

The mayor of Barcelona, the region's capital, said more than 460 people had been injured in clashes between police and voters.

Officers have used batons and - in one incident in Barcelona - rubber bullets to remove people from polling stations across the region, with separate footage showing police seizing ballot boxes and smashing their way in to polling centres.

Police broke down doors to force entry into voting stations as defiant Catalans shouted 'Out with the occupying forces!" and sang the anthem of the wealthy northeastern region.

The aggressive tactics of Spanish authorities have prompted widespread and growing international condemnation.

Belgium's prime minister, Charles Michel, called for political dialogue in Spain and tweeted "violence can never be the answer!"

Scottish National Party leader Nicola Sturgeon said: "Regardless of views on independence, we should all condemn the scenes being witnessed."

Labour Party leader Jeremy Corbyn said: "Police violence against citizens in Catalonia is shocking. The Spanish government must act to put an end to this now."

And Slovenian Prime Minister Miroslav Tserar said he was "worried" about the situation.

"I call for political dialogue, the rule of law and peaceful solutions," he said.

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

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.

"I'm so pleased because despite all the hurdles they've put up, I've 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 Spain's 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.

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.

Additional reporting by agencies