Unionists clashed with separatists as thousands of Catalans took to the streets and a pro-independence radio station was attacked with journalists forced to barricade themselves inside.
It is feared a further descent into violence could be triggered if Catalonia’s separatist executive refuses to step down or the police force fail to take orders from Madrid.
The prime minister has stripped Catalonia’s most senior police officials of their powers, including the force’s leader, and called snap local elections for December 21.
The central government has also taken control of its civil service, finances and public media.
Spain’s top prosecutor has warned that the local politicians responsible for the independence vote could face treason charges and up to 25 years in jail, with arrests planned for as early as Monday.
Prime Minister Mariano Rajoy said at around 7.30pm UK time: ‘Spain is living through a sad day. We believe it is urgent to listen to Catalan citizens, to all of them, so that they can decide their future and nobody can act outside the law on their behalf.’
‘Today, the Catalonia parliament has approved something that in the opinion of a large majority of people not only goes against the law but is a criminal act.’
The announcement was met with jeers and whistles outside the government palace in Barcelona, where thousands have been celebrating the independence declaration.