On the afternoon of the terrorist attack in Barcelona, Fatima El Himer, 17, and her sister Haffssa, 20, had gone shopping in the center of their hometown Granada. They were about to catch the bus back home when Fatima noticed a group of Spanish ladies talking about them.

"We overheard them say that it was a disgrace that we were out here shopping while in Barcelona people had died because of people like us," she says. "I was shocked. I had never heard anyone say anything like it before."

Read more: Terror attacks leave Barcelona and Madrid at odds, as ever

The sisters were small children when they moved with their parents from Morocco to Granada. Fatima says she has always felt very welcome. "No one in Spain ever treated me differently because I wear a hijab. The attacks that happened in France, Belgium and the United Kingdom over the past few years did not change that. On the contrary, a lot of people said that they knew these attacks had nothing to do with me."

But something has changed since the August 17 attacks in Barcelona and Cambrils that left 16 people dead.

"For the first time in my life I feel uncomfortable when I am out in town. People look at me in a suspicious way because of the hijab I wear. The other day a passerby shouted that I should stop hiding things under it," she says.

Fatima is not alone. Muslims across Spain have reported an increase in anti-Muslim sentiment and hate crimes since the Barcelona attacks. Graffiti has appeared on mosques in Granada, Madrid, Seville and Tarragona that read: "You are going to die" and "Murderers you will pay for this!" 

Read more: Catalonia's Islamic extremism problem

Four days after the attacks, 2,500 Muslims took to the streets of Barcelona to denounce terrorism. Many of them held banners reading: "Not in my name" or "Terrorism has no religion." Madrid's Muslim community held a similar demonstration in a central city square on Friday.

Hate on the rise

But their message is not being heard by everyone.

"The xenophobic storm that has been unleashed on social media is incredible," says Mounir Benjelloun, president of the Spanish Federation of Islamic Religious Entities. "Of course many Spaniards are afraid after what happened in Barcelona. But right-wing extremist groups have taken advantage of this fear to disseminate hatred against all Muslims."

SOS Barcelona, which works to eradicate xenophobia in the city, has received a significantly higher than usual number of reports from Muslims who have been insulted or threatened on Facebook, according to spokesperson Monica Lopez. "It's still too early to say what this means for the long term," she says.

Unlike in much of the rest of Europe, far-right parties have not gained a foothold in Spain. But xenophobic and Islamophobic incidents have increased since the deadly attack on the French satirical weekly Charlie Hebdo in Paris in January 2015.

Read more: Spain proves sterile ground for far-right parties

"Every time a terrorist attack has been committed somewhere in Europe, the number of hate incidents against Muslims in Spain has risen immediately," Benjelloun says. A recent study by Spain's Citizens Platform against Islamophobia found that the number of Islamophobic incidents had shot up from 49 in 2014 to 567 last year.

'Islamophobia is contagious'

It's striking how different Spanish society reacted after the Madrid attacks in March 2004, when 192 people died, Benjelloun says.

"Back then people knew that the terrorists who committed the attacks had nothing to do with the Muslim population in Spain itself. Now more and more people seem to find it difficult to make that differentiation." 

Chafik El Boudali, 35, the owner of a fruit and vegetable shop in the Madrid neighborhood of Tetuan, says some of his usual customers have stayed away since the Barcelona attack. "I don't know what they think," he says. "That we are all terrorists? But what has happened in Barcelona has nothing to do with Islam as I know it." 

A few blocks away, Mohamed Tazet, 47, a Moroccan who owns a butcher shop right in front of the local mosque spoke of a Moroccan woman who had been attacked in the subway last week. "Many Moroccan women now fear that something similar may happen to them."

Despite the rise in Islamophobic incidents, Benjelloun believes most Spaniards are tolerant people who are aware that the majority of Muslims condemn terror just as they do: "Look at what happened in Barcelona: The day after the attacks, a right-wing extremist group demonstrated against Islam in the Ramblas area, where the attack took place. Local residents blocked the streets to prevent them from entering the area and chased them away by confronting them."

Benjelloun strongly believes the Spanish state should take measures against the far right. "You cannot just wait until this fades way, because it won't. Islamophobia is very contagious. The state should prosecute those who spread hatred and intolerance."