Protestors from the Catalan separatist movement Democratic Tsunami have called for a “massive” protest outside Camp Nou, where Barca are due to play the match against Real in La Liga on December 18.
Spain's most prestigious fixture was originally scheduled for October 26 but had to be postponed following a wave of pro-independence demonstrations in Barcelona which saw protesters hurl rocks at security forces and set up fiery barricades.
Police “will guarantee that the match goes ahead, fan access to the stadium and security both on and off the pitch,” the Catalan interior affairs chief, Miquel Buch, told a news conference.
Around 1,000 officers from Catalonia's regional police force, the Mossos d'Esquadra, will be deployed along with 2,000 agents from other police forces and private security agencies, Mossos chief commissioner Eugeni Sallent added.
The deployment is usual for matches deemed “high risk” but this time it was boosted by “hundreds” of extra agents both inside and outside the statement because of the call to protest by Democratic Tsunami, he added.
The agents will guard the vicinity of Camp Nou beginning on Wednesday morning to ensure the teams, referees and fans can enter the stadium without problems.
They will also cordon off the area to ensure demonstrators can not get close to the stadium.
Democratic Tsunami has urged protestors to gather at four points around Camp Nou from 4:00 pm (1500 GMT), four hours before kick-off.
'Complex scenario' of pitch invasion
The group denied Friday on Twitter it wanted to “block or suspend the match”.
“On the contrary, we want to invite the whole world to see it,” it added.
Thousands of people have registered their interest online in attending the protest action.
“One of the most complex scenarios would be an invasion of the pitch. It is an extreme situation which in principle we don't contemplate as being probable but it is possible,” said Sallent.
Democratic Tsunami has in the past blocked access to Barcelona's airport and cut the main highway linking Spain to France for two days.
The planned rally at Camp Nou is the latest in a series of demonstrations that began two months ago when Spain's top court jailed nine Catalan separatist leaders over their role in a failed 2017 bid for independence.
If a pitch invasion were to take place then Barcelona, who are responsible for security inside the stadium, could face hefty fines and be ordered to stage future matches behind closed doors.
Barca have long been associated with Catalan independence.
The club's fans often wave the yellow and red striped Catalan independence flag and hold up banners at Camp Nou proclaiming in English that “Catalonia is not Spain”.
Real on the other hand are associated by many Catalans with the perceived centralising force of the Spanish government in Madrid.