Earlier, Spanish media reported that police have detained protesters in Barcelona and used rubber bullets to disperse them.
"The violent response of the Spanish state to the referendum is undemocratic".
Soon after the polls opened, Spanish riot police smashed into the voting centers, their raids caught on mobile phone cameras that showed them whipping citizens with rubber truncheons and dragging them away by their hair.
"I would urge the global community to speak out against Spanish efforts to violently prevent a democratic referendum".
Catalan President Carles Puigdemont said that if a "Yes" vote was recorded, the region would move towards independence within 48 hours. Despite the riots, which drew global criticism, Spain's Prime Minister Rajoy praised the police: "They were doing their job- to uphold the law", he said. Catalonian authorities intended the vote to be a democratic method of moving towards total independence.
Voter turnout was about 42 percent in Catalonia which has an electorate of 5.3 million voters.
Should a vote against independence be returned, it is likely a new round of Catalan regional elections will follow.
Catalonia, a wealthy region of 7.5 million people in north-eastern Spain, has its own language, culture and regional government - or Generalitat - which already has considerable powers over health care, education and tax collection.
Police officers prevented some people from voting, and seized ballot papers and boxes at polling stations. He added that 15,000 votes were still being counted.
The Spanish government declared the referendum unconstitutional prior to the vote and now says it was successfully disrupted.
"Catalan authorities said 319 of about 2,300 polling stations across the region had been closed by police while the Spanish government said 92 stations had been closed", the BBC reports.
Spanish Foreign Minister Alfonso Dastis said the violence, while "unfortunate" and "unpleasant" was "proportionate".
Rajoy thanked security forces for upholding the law and doing their job.
The massive police crackdown "prevented" an estimated 770,000 people from voting, Catalan government board member Turull said during the vote result announcement.