Muslim leaders in Spain called for calm ahead of Tuesday's crunch World Cup decider between Spain and Morocco amid fears of a repeat of crowd trouble in Belgium last week.
Photographs and videos showed cars being smashed and upturned, and fires started in Brussels in the wake of Belgium’s shock 2-0 defeat to Morocco in Qatar.
The riot police fired water cannons and tear gas to disperse crowds and subway and tram traffic was halted.
Police reinforcements have been increased in Madrid and other parts of Spain ahead of the match in case of trouble.
There is concern that far-right groups like Vox, which is the third largest political force with 52 lawmakers in parliament, may stir up trouble.
Violence among Moroccans living in Spain is extremely rare but the two countries are near neighbours and political tensions have existed in the past over issues like illegal immigration.
Rabat still claims Melilla and Ceuta, the Spanish enclaves in North Africa, as Moroccan territories.
More than 870,000 Moroccan nationals live in Spain, making them the largest group of foreign nationals followed by Romanians and Britons, according to government figures. Many more descendants of Moroccans have become naturalised Spaniards.
There are large communities of Moroccans in the northeastern region of Catalonia, Murcia in the southeast and Almeria in the deep south.
Ahmed, who comes from a Moroccan family but who grew up in Madrid, said he was angry that Moroccans were suspected of being troublemakers.
"It makes me fed up that there are people who can cause these riots and who blame Moroccans. If you are in a country looking for a better life, do not tarnish the image of the rest," he told El Mundo newspaper.
'Enjoy the match whoever wins'
Abdallah Mhanna, the Imam in the Almuhseneen mosque in the centre of Almeria, said most fans would enjoy the match but a few could cause trouble.
"The vast majority of Spaniards or Moroccans will just enjoy the football whoever wins. But there might just be two idiots who might not be able to control themselves and they will create problems. This could blow up if the other side reacts to this,” he told Euronews.
“We would appeal to Muslims to use the core values of Islam of peace and non-violence to ensure that nothing happens, and we can simply enjoy the match whoever wins.”
The Imam said that about 70,000 Moroccans live in Almeria, with many working on farms producing vegetables which are sold across Europe. He said many of these people had attained Spanish nationality.
“There will be some who support Spain and others who support Morocco. What matters is that they enjoy the football,” he added.
The Spanish Federation of Islamic Religious Entities issued a statement calling for calm among all supporters of Morocco.
“Whatever the result, whether it be a pleasure for some or a sadness for others, (that) the demonstrations cannot produce public disorder which will prejudice our neighbours or the local area which is for the use of everyone," the statement read.
“Sport, in the case of football, has to serve the principles of Islam, which is respect, tolerance and coming together and not division.”
Police and far-right target Moroccan fans
Spain’s National Police and Civil Guard, the two main national forces, said in an operational note sent to regional stations that there was a possibility of “celebrations and altercations after the match on December 6 would lead to trouble”.
The note added that it was difficult to estimate the number of officers who could be needed but the only way this could be gauged was by checking the number of Moroccans who were registered with local councils.
Hardline supporters of Seville and Betis, another team in Seville, tweeted to say they will defend their city against any "vandalism by Moroccan supporters".
Rocio de Meer, a lawmaker for Almeria for the far-right party Vox, targeted fans in a nearby town where an estimated 65% of the population is originally from Morocco.
She posted a tweet which showed Moroccan fans celebrating after an earlier World Cup match in El Eljido and asked: “Who will be brave enough to celebrate a Spanish goal in Calle Manolo Escobar in El Ejido?"
Nadia Otomani, of Al Anwar Association of Moroccan Women, said: "There is a group which has rage inside them. They are rejected by the majority of Moroccans themselves."