Catalan independence vote begins in chaos as police seize ballot boxesA man tries to talk to a civil guard at a Catalan referendum polling station in Sant Julia de Ramis, near Girona, Spain

Barcelona, Spain (CNN)Catalonia's disputed independence vote quickly descended into chaos on Sunday as Spanish national police entered polling stations, seizing ballot boxes and voting papers.

In the town of Girona, where the regional President Carles Puigdemont was due to vote, police smashed their way into a polling station by breaking a glass window.

Spain's national government is implacably opposed any breakaway moves by the northeastern region, and the country's top court declared the vote illegal. "Police are confiscating ballot boxes to respect the judicial mandate and the law regarding the illegal referendum," Spain's interior ministry said in a Twitter message.

In Barcelona, lines of Guardia Civil attempted to prevent voters from entering polling stations, photographs showed.