Riot police in Barcelona clashed with protesters outside the highly anticipated Barcelona-Real Madrid soccer match Wednesday evening, as authorities sought to prevent the stadium from becoming an ideological battleground for Catalonia’s separatist movement.

The match in Barcelona's Camp Nou stadium, viewed by 650 million people worldwide, began without incident. It was briefly halted when fans threw balls onto the field with messages for the Spanish government to open a dialogue with the separatists.

Thousands of police and private security guards were deployed in and around the stadium.

Outside, riot police used batons to force the crowd back. Some of the protesters threw objects at officers lined up behind shields, while others fought among themselves.

There was no immediate word on possible injuries.

The game, which had been postponed from Oct. 26 amid violent protest by the separatists, drew nearly 100,000 spectators and ended in a scoreless draw. Fans were directed to leave through the stadium's south side to avoid the clashes outside.

Catalan separatists had sought to promote their independence bid by using media coverage of the game between Barcelona, the Spanish league leader, and its fierce rival Real Madrid.

As the game began, some fans held up blue signs saying "Spain, Sit and Talk" and "FREEDOM," while others chanted, in Catalan: "Freedom for the Political Prisoners."

Those messages referred to the Spanish government's refusal to discuss the region's independence, as well as the recent imprisonment of nine of the movement's leaders convicted for their roles in a failed secession bid.

The Barcelona team had asked its fans to behave with civility and not to affect the match. The U.S. Consulate in Barcelona had advised people to avoid the area if possible.

Separatist sentiment has grown substantially in Catalonia since the global recession. Polls and election results show that the 7.5 million residents of Catalonia are about equally divided by the secession question.

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Separatists have used the Camp Nou stadium as a protest platform for years. They shout "Independence!" at a set time during matches and sometimes unfurl banners.

The Barcelona team has pivoted between supporting its fans' right to free speech and aligning itself with the greater interests of Catalonia. Many feel it does not fully support secession so as not to anger its Catalan fans who are not separatists or its millions of supporters across Spain.

Its rivalry with Real Madrid has a decades-old political undercurrent, with many Catalans seeing the capital's team as a hallmark of Spanish unity and authority.

Players from both teams usually get along. The Spanish national team that won the 2010 World Cup and two European Championships was packed with players from both sides.

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Security is always high whenever the teams play -- just like at many soccer matches between fierce rivals -- but there is no history of violence at the games.

The Associated Press contributed to this report.