Supporters of the jihadist group “Islamic State” [IS] have clashed with Kurdish Yazidis in North Rhine-Westphalia, the state with the largest Muslim population in Germany.

The violence—which comes amid threats by a German jihadist to blow up an American nuclear weapons storage facility in Germany—has counter-terrorism officials concerned that radical Muslims are deliberately exploiting the ethnic and religious tensions in the Middle East to stir up trouble on the streets of Europe.

Police say the Muslim-Yazidi clash was triggered after six Islamists stormed a restaurant in the eastern Westphalian town of Herford at around 4 pm on August 7. The Muslims were attempting forcibly to remove a poster inviting people to join a demonstration in support of the Yazidis in Iraq.

Thousands of Yazidis, an ethnic Kurdish non-Muslim minority, were forced to flee their homes in northern Iraq in early August to escape advancing Islamic State fighters, who are forcing the Yazidis to convert to Islam or be killed.

The 30-year-old owner of the restaurant in Herford and two others, all Yazidis, were injured in the brawl, which police say was fought with knives and bottles.

Several hours after the restaurant attack, between 300 and 500 Yazidis gathered in the Herford town center, where they clashed with a large group of hooded Salafists.

More than 100 police reinforcements from across eastern Westphalia were called in to restore order. Police, who used pepper spray to disperse the two groups, confiscated makeshift weapons and one firearm, and questioned 86 people.

In the final tally, police arrested six individuals involved in the attack on the Yazidi restaurant: Five ethnic Chechen Salafists and one German convert to Islam. According to German media, two of the individuals are leading Salafist operatives who were already being monitored by German intelligence.

A German intelligence official was quoted as saying that one of the Chechens is a trained fighter who participated in guerrilla warfare against Russian troops and who is considered to be “highly dangerous.”

German authorities have long warned of the threat posed by Salafism, a radically anti-Western ideology that seeks to impose Islamic sharia law in Germany and other parts of Europe.

Membership in Islamic extremist groups in Germany rose to 43,185 in 2013, up from 42,550 in 2012, according to German intelligence estimates. The number of Salafists in Germany rose to 5,500 in 2013, up from 4,500 in 2012, and 3,800 in 2011.

Although Salafists make up only a fraction of the estimated 4.3 million Muslims in Germany, authorities are increasingly concerned that most of those attracted to Salafi ideology are impressionable young Muslims who are susceptible to perpetrating terrorist acts in the name of Islam.

North Rhine-Westphalia is home to the largest concentration (about 1,500) of Salafists in Germany. The region is also home to most of the estimated 60,000 Yazidis who live in Germany.

The area around Herford has long been a magnet for Salafists, and mosques in the town are known to convert young people to Salafism. “Even the operator of a fitness center is suspected of wanting to inspire young Germans, under the guise of sports, for Salafism,” an intelligence official was quoted as saying.

More than a dozen men from the Herford area have joined IS in Syria and Iraq, and at least one, a 22-year-old German convert to Islam, is known to have been killed in the fighting.

On August 7, a German jihadist from the Westphalian city of Essen, who is believed to be fighting in Syria,threatened to bomb the American nuclear weapons storage facility situated near the city of Koblenz. The 27-year-old convert to Islam, who is known as Silvio K., also threatened to attack churches, government agencies and transport networks across Germany.

A German Interior Ministry spokesperson said that although “the threat is abstract, it may become real at any time.” He said it proves that Germany “is still the focus of jihadist terrorism,” especially from jihadists returning from Syria with combat experience and contacts to jihadist groups.

German commentators have reacted to the events in Herford with a sense of foreboding, with some saying that the war in Syria and Iraq has now arrived on Germany’s doorstep.

In an editorial entitled, “The Madness Reaches Eastern Westphalia,” the newspaper Westfalen-Blatt states:

“The Yazidis deserve our sympathy and support as do any other oppressed people in the world. The call for participation in a demonstration against genocide, which triggered the events in Herford, is perfectly legitimate in a democracy. It is to be hoped that many German flags will be flown at the rally to protest the misuse of religion for political purposes. Hopefully Herford is not the beginning of an escalation that could reach further levels of violence over the next few days….

“And this is frightening: Never before have the sympathizers of Islamic terror appeared so openly in Germany. These are the circles in which European fighters are recruited for jihad. This is also the milieu in which the Salafist ultra-radicals develop when they are back in Europe again. Therefore, police and secret service are required to monitor the scene closely.

“And no, we did not know that Chechen Muslims are such vehement supporters of the IS-terrorists in Iraq. The Chechens in the southern Russian Caucasus are themselves victims of repression and human rights violations.

“IS, Al-Qaeda, Hamas and Boko Haram—these four groups are the linchpins of the attempt to bomb an unstoppable modernity back into the Middle Ages. The means to this end are Sharia, hatred and glorification of a supposedly “holy” war—what madness!”

The newspaper Neue Westfälische stated:

“When—if as now in Herford—the Kurdish Yazidi religious community and the radicalized Islamist ideology of the Salafists collide, then a city in eastern Westphalia is in danger of going up in flames.