Catalonia's independence referendum has descended into chaos, with clashes occurring as police attempt to prevent the vote from taking place, BBC reported.

The Spanish government has pledged to stop a poll that was declared illegal by the country's constitutional court.

According to BBC, police officers are preventing people from voting, and seizing ballot papers and boxes at polling stations.

In the regional capital Barcelona, police used batons and fired rubber bullets during pro-referendum protests.

Catalan emergency services said they had treated 38 people who were injured when police pushed back crowds of voters and forced their way into polling stations.

The Spanish interior ministry said 11 police officers had been injured.

Catalan leader Carles Puigdemont condemned the action of the national police and Guardia Civil, who were sent into Catalonia in large numbers to prevent the vote from taking place.

"The unjustified use of violence... by the Spanish state will not stop the will of the Catalan people," he told reporters.

But Spanish Interior Minister Juan Ignacio Zoido blamed Mr Puigdemont for what he termed the day's senseless events.

And the Guardia Civil tweeted (in Spanish) that it was "resisting harassment and provocation" while carrying out its duties "in defence of the law".

How is the day unfolding?

The ballot papers contain just one question: "Do you want Catalonia to become an independent state in the form of a republic?" There are two boxes: Yes or No.

Ahead of the polls opening, the Catalan government said voters could print off their own ballot papers and use any polling station if their designated voting place was shut.

In the town of Girona, riot police smashed their way into a polling station where Mr Puigdemont was due to vote.

Television footage showed them breaking the glass of the sports centre's entrance door and forcibly removing those attempting to vote.

However, Mr Puigdemont was still able to cast his ballot at another polling station.

Since Friday, thousands of separatist supporters had occupied schools and other buildings designated as polling stations in order to keep them open.

Many of those inside were parents and their children, who remained in the buildings after the end of lessons on Friday and bedded down in sleeping bags on gym mats.

In some areas, farmers positioned tractors on roads and in front of polling station doors, and school gates were taken away to make it harder for the authorities to seal buildings off.

Referendum organisers had called for peaceful resistance to any police action.