Activists, protesting against right-wing violence, demonstrate in the city centre five days ahead of the beginning of the NSU murder trial on April 13, 2013 in Munich, Germany. (Photo by Johannes Simon/Getty Images)

While U.S. agencies continue to focus on anti-Western Islamist terrorists, their German counterparts have recently been forced to investigate the opposite: anti-Muslim terrorism.

On Wednesday, authorities raided homes across Germany and took four anti-Muslim terrorism suspects into custody. They are accused of having planned attacks on mosques and asylum seekers.

The suspects — who had recently founded a group called "Oldschool Society" — are believed to be right-wing extremists. "The four arrested procured explosives for possible terror attacks by the group," a statement by German police authorities specified. According to Germany's Der Spiegel magazine, a first terror plot on a refugee housing center might have been imminent.

This would not have been the first anti-Muslim terror attack in Germany

Germany is still dealing with the fallout of anti-Muslim terror group National Socialist Underground (NSU) which killed 10 people – most of them Turks – between 2000 and 2007. Back then, investigators had blamed Germany's immigrant community for most of the deaths and portrayed them as the result of infighting and organized gang crime.

Two of the suspected terrorists later killed themselves; a third, Beate Zschäpe, is currently on trial in Munich. Their attacks have led to deep mistrust between Germany's large immigrant community and state officials: The country's intelligence services stand accused of having deliberately ignored hints that the attacks had been committed by right-wing extremists.

The photo taken from the Facebook page of "Oldschool Society" on May 6 shows the logo of the group. (OSS via AP)

Speaking about Wednesday's arrests, German interior minister Thomas de Maiziere said: "If the allegations are true, this would be the first group of its kind following the NSU."

Contrary to Spain, France or Great Britain, Germany has been spared from an Islamist terror attack on its soil and targeting German citizens in recent history. Investigators do say that they have prevented numerous attacks: Last weekend, authorities cancelled a popular bike race in western Germany because they feared an Islamist attack.

Are German authorities 'blind on their right eyes'?

It seems striking, however, that the only terror group which was able to kill without being held accountable for years was not an Islamist organization but a right-wing extremist German group, primarily targeting Muslims.

In recent months, new details emerged which have led to questions whether Germany's ignorance of the far-right threat might be even bigger than first assumed.

After the NSU group's alleged crimes were revealed, a review of thousands of cases brought to light that 849 more people than originally thought could have been killed by right-wing extremists since 1990. Critics say that authorities ruled out right-wing extremism as a motive for those killings, despite evidence suggesting otherwise. Whether or not those incidents could now be categorized as victims of right-wing terrorism is uncertain, though.

Some Germans draw parallels between the most recent attacks and the early 1990s, when a wave of attacks hit centers and houses­ for foreign workers, as The Post's Anthony Faiola reported in April.

“They don’t belong here,” Ronny Seyfert, a 39-year-old part-time gardener in Tröglitz, told The Post earlier this year -- echoing an anti-immigrant sentiment that has worried politicians and civil society leaders alike.

Germans, like many other Europeans, are increasingly opposed to the rising number of immigrants seeking asylum in their countries.

Other countries have also dealt with incidents of anti-Muslim attacks, although it is disputed to what extent they would be categorized as terrorism. In July 2013, for instance, a nail bomb exploded in front of a mosque in Tipton in the West Midlands. Although nobody was injured, the BBC quoted police official Gary Cann describing the incident as an "act of terrorism."

In January, The Washington Post reported that French Muslim leaders had counted more than 50 anti-Muslim attacks within the week following the attacks on the editorial offices of Charlie Hebdo and a Jewish supermarket in Paris.

The number of French saying that their country should accept fewer immigrants amounted to 57 percent in a 2014 Pew Research Center survey. Forty-four percent of Germans agreed, whereas in Italy and Greece, anti-immigrant sentiments were especially high, with 80 and 86 percent respectively.

Contrary to other incidents reported throughout Europe, German right-wing groups have operated with shocking precision and long-term planning.

In Germany, right-wing extremists seem to be especially well connected

According to investigators, German right-wing extremists rely on a network which has grown over decades. German intelligence services are believed to have hired some of the extremists as double agents, which has led to an explosive intertwinement of state authorities and criminals.

The revelations have so far not significantly lowered the risk Muslims and other immigrants might face in Germany: In 2014, refugee centers were attacked about 150 times in the country, according to a recent report by the Amadeu Antonio foundation. In April, unknown suspects burned down a house in eastern German Tröglitz which was set to become an accommodation for asylum-seekers. Compared to 2013, violent crimes by right-wing extremists were up 22.9 percent in 2014. Anti-Semitic attacks also increased.

Germany's interior ministry released a report Wednesday which blames anti-Muslim movements such as PEGIDA for the rise in attacks. Indeed, Kathrin Oertel — one of the former heads of PEGIDA — recently apologized to German Muslims for causing a "campaign of hatred."